Carbed 280z Bogging Issue

[Italian]

Heres the fuel pump, which after some research I think may be the root of the problem.

 

 

I looked up the pump and it has a flow rate of between 23 GPH and 32 GPH, which sounds quite low to me. On top of that, the inlet/outlet are 1/8" fittings, which seems quite small. Plus it would explain why the bogging happened more after hooking up a return line. Previously, the fuel could only go to the carbs, whereas now it has a place to escape. 

 

The wiring shouldn't be an issue as the entire car was properly re-wired in March. Theres a fuse on the fuse panel, as well as an internal fuse in the pump, at least according the the Facet website. 

 

Heres the new routing of lines and the FPR:

 

 

 

The line that appears to be coming/going off the right side of the first photo is the brake booster vacuum line, not a fuel line. The fuel filter is the round matte grey can in the second pic.

 

The fuel pressure gauge was reading ~2.5 PSI when I took the photos, which was about 20 minutes ago, and the pump hasn't been on since Sunday evening/ Maybe the gauge just needed to "break in" somehow, which I've never heard of a gauge needing to do but it would explain why it read nothing over the weekend.

 

I haven't checked float level, but I could do that next weekend (hopefully).

 

The stock volt meter is still in the car, but I can' say how accurate it is. It seems to red between 12 and 14 volts depending on the day. One thing I can say about the electrical stuff is that when ever the car bogs and I kill the engine, I have the star the car by letting the clutch out. If I try to start it using the starter with the clutch in, it sounds as though the battery is dead. I have no idea why it does that, the battery is new, wiring is new, and the car starts just fine after sitting for a week and a half (Longest I've left it dormant since the rewire).

 

 

Right now I'm thinking the most likely issue is the fuel pump. I plan to and have started buying stuff to completely re-do the fuel system, so I could just focus on getting a new pump right now rather than after all the fittings and lines.

Edited April 22, 2014 by Italian

[seattlejester]

Actually the fuel flow rating is quite high. I was told 1gph can feed ~10hp on the high side by pegasus racing when I was looking around. So that pump should be able to feed 230-320hp. I had a 15gph in my car and it ran fine until the fuel relay spade fell off.

 

I recall the bottom one had the restrictor in place. Did you check the lines to make sure the restrictor is either removed (if you are using the regulator, which it looks like you are) or plumbed to the correct line?

 

The voltmeter should be reading high 13 or 14's unless you are using an accessory. Not being able to use the starter to start the car seems strange. I could crank mine for a minute or two on my tiny battery. Alternator checks out?

 

Three things to do is one, pop off the return past the regulator and turn the pump on (make sure you have a bucket so the gas doesn't eat the paint). You should see good fuel flow once the pressure is reached. Next try the same with the feed line popped off. Finally try it with the filter popped off. Each time the flow should be roughly equivalent and the gas should be the same color. My thought is the gas coming post filter is going to be milky and the filter may be filled with gunk. If that is the case, you may want to swap the filter near the pump as well.

 

It could very well be the pump, a replacement is 40$ or so, and it comes with a new filter, that may not be a bad idea. I would get a clear filter in the engine bay at least for testing so you can see the fuel actually moving around.

[Italian]

Hmm, well alright then. Either way, theres still the possibility that it might be on its last legs. One of the days when it was happening the pump was absurdly loud, so much so that it could be heard over the exhaust (which is quite loud). Also the noise it makes is like a rapid thumping, like a really muffled motorbike type of rapid thumping. Is that abnormal? I've always ever heard the buzz of an electric motor, never a thumping type of sound.

 

I have no idea whether or not the restrictor is in there. I could check hopefully over the weekend. Could I just take those hard lines off and try to pass some liquid through one (hold the line vertically, pour liquid in the top) and see if one flows less? 

 

It usually does read around 13 or 14, and I haven't noticed any correlation between the differences in voltage and the bogging. The volt meter has ticks at 12 and 16, so I can really only guess the values, but still. There seems to be a mild inconsistency in the voltage. The alternator was replaced with a rebuilt 280zx unit a year and a half ago, so I would assume it's in OK condition.

 

I'll see if I could do that this weekend, though it may have to wait till next. 

 

Would trying to get an idea of flow rate be a good way to test the pump? Like time how long it takes to pump out a gallon then figure out the GPH based o that?

[seattlejester]

It is a physical restriction, you would just take the rubber line off and look at the connection to the fuel rail. One tube should have no restriction, the other will have a much much smaller hole. 

 

It's up to you really. If it is worth your time to test the flow rate then go for it. If you would rather spend 40$ and not worry about it then go that route. For all we know it really could be a tired pump, or maybe a worn pump, it may indeed not be pushing adequate fuel so your bowls run dry. This is all still assumption though. Checking that your carbs are functioning correctly would be the next step after you check the pump and change out the filters. 

 

From the fuel perspective it could only be....

Electrical (you said a recent rewire should prevent that from being an issue)

Fuel routing (you took care of that with the reroute)

Fuel tank (rust in the tank clogging the pickup or bits coming loose and...)

Clogged filter (clogged filter would mean even with pressure behind it only so much can go)

Fuel pump (really tired or worn fuel pump could indeed be winding down or not delivering the promised volume)

Fuel metering device (carb setting, a really badly set float could be shutting the fuel flow off prematurely making the small amount of fuel in the bowls run out very quickly before needing to be filled again)

Engine (low engine vacuum could mean that even if your fuel flow and metering was perfect, the engine is not pulling sufficient vacuum to pull a vacuum across the carbs to pull up the fuel)

Low fuel (I highly doubt that is the case, I'm sure that is one of the first things you checked if different amounts of fuel in the tank alleviated the problem)

[Italian]

Ah alright, I'll check that. should that be the case I'll just make a run to the hardware store and pick up some more fuel line and get rid of the hardline.

 

I might just get a new pump then anyways. At the very least, it might reduce noise. 

 

Float level check will take place this weekend for sure.

 

So from that list:

 

Electrical: Good

Fuel routing: Good

Fuel tank: Definite Possibility

Clogged filter: Definite possibility, will replace both

Fuel pump: Plan to replace anyway, will buy sooner than planned

Fuel metering device: Checking this weekend

Engine vacuum: Good. I rebuilt the engine last summer and have put ~2000 miles on it. It pulls a very strong vacuum

Low fuel: I haven't noticed any difference when there was more fuel in the tank than less, but this sparked another idea. The fuel gauge seems to be off a good bit, and when I took the picture of the pump it looked like it had been bashed in a bit. With those things in mind, theres a possibility that the feed for the pump is no longer at the lowest point of the tank. I'll check it again and make sure that this isn't the case.

[seattlejester]

I believe you can just cut the end off, it's literally just a small restriction at the very end of the pipe. Other then that, it seems you have a good list and plan. Really hope we will hear good news next week.

[Italian]

Update:

 

Starting the car today I noticed the fuel pressure gauge was reading 1, maybe 2 PSI at best when I just had the pump going. This could either be due to the FPR being inaccurate, or the fuel system not being able to flow enough fuel or maintain any higher pressure. Since it needed to be done anyway, and, well, since I already had the parts, I'm going to eliminate the flow side of the equation. It also ended up being the cheaper route  Whilst driving the car it bogged a lot less than the last time I drove it, and I noticed it really only did so when I held the car at a speed where the engine was revving over 3000 rpm. If I kept it under that, it seemed to be just fine. Anything over it though, and it bogged pretty quickly.

 

I checked the fuel hard line in the engine bay (bit that goes around the front of the cam cover) and there were no restrictions, so that is ruled out as a possible cause of the bogging. However, I noticed that the inside of the hard liens were rusted and dirty, so I'm going to remove them completely and put 5/16 hose in their place. Won't look the best, but it'll do for the 1 or 2 months before I re-do everything with AN lines.

 

I ordered a Holley Red pump as well as some filters to install this weekend. The current filters being clogged was another possible cause of the bogging, and the fuel pump being already pretty low flow and possibly on its last legs was another. New filters will free up some flow for sure, plus they're both clean so I can see if they're clogged. On top of that, a new pump with nearly 4 times the free flow rate should definitely help.

 

 

 

 

I installed the fittings on the pump just earlier today so that the thread sealant has time to set up before I install the pump. This will also give me time to prepare everything for the install. Container to hold the fuel in the tank, make sure I have all the line and clamps I'll need, figure out wiring, and possibly secure a lift to make the job go a whole lot smoother.

 

 

 

I have not checked the float level yet as I realized if I did have to adjust it, I'd need new gaskets for the float bowl lids and since I don't have any spares, it'd have to wait anyway.

 

 

Hopefully I'll have good news after the weekend!

Edited May 2, 2014 by Italian

[Italian]

Heres all the useful info from over the weekend:

 

 

 

When I was draining the tank, there was but a trickle of fuel coming out using the fuel pump. 

 

 

 

This pretty much confirms the suspicion of poor fuel flow. I then went and disconnected the hose that goes from the return line to the tank and let the fuel drain out of there. 

 

Next were the filters and some hose. The source of the issue showed itself upon firing up the pump for the first time. A whole hell of a lot of sediment filled up the pre-pump filter immediately. 

 

 

Then the post-pump filter wasn't filling up, but from a little of what I've read I think that is normal.

 

 

 

 

I'm going to figure out a way to drain the tank and try to get all the sediment out, as well as clean out that pre-pump filter. Hopefully I can figure that out before June. The car is running horribly and I believe it's due to the poor flow. Especially considering I could only get a max of 1 PSI of line pressure. 

 

If anyone has advice on draining the tank and cleaning it without dropping it, I'd love to hear it.

[seattlejester]

That's good some real headway.

 

The post filter on my car never filled up. It bothered me, too as I would expect it to.

 

Unfortunately most solutions will require dropping the fuel tank.

 

The cheap method is to DIY rock tumble the inside via pouring gravel into the tank with a bit of solution (can't remember exactly what it was) and then shaking the bajebus out of it. Method is readily viewable on youtube I believe. 

 

More professional method would be to tank it to a radiator/tank shop and see if they could do it for a reasonable fee. Most places can sonicate to loosen the rust, clean out, acid treat and coat the inside. If the shop is thurough and familiar with tanks they may even separate the tank to really get in there.

 

Without cleaning out the tank you are kind of at the mercy of time. You can try manually pump some evapo rust or something in there, but any big sediments or chips are going not necessarily going to drain out of the drain hole. And it will just be a matter of time before the sediment/chips break down, moves around, and gets picked up.

 

The only difficult part of dropping the tank is all the hose connections, the tank is just held in with a couple straps held by J-bolts. I think it would be a very good piece of mind to clean it out off the car even if not very much comes out.

[Italian]

Its so odd how that works isn't it.

 

 

I know for sure I will be dropping the tank and having it professionally taken care of in the summer once I'm home from school, but right now my biggest concern is getting the car/tank in a condition where I could drive it the 510 mile trip home once school gets out. I might be able to get it professionally taken care of up here, but its a big might.

 

Obviously there is a lot of sediment in there now, but how long does it take for a decent amount of sediment to build up? I'd assume it varies with tank condition and such, but if I could get all the sediment out of there now, or as much as I can, and make the car drivable for the next month without worrying about having too much sediment build up again I'd be happy. Would that be a possibility?

[seattlejester]

You have to think a bit, how did sediment get in your tank. Unless you have been putting sand in with your fill ups, or it sat around for quite a while with the gas tank open, it unfortunately is probably rust. If you can get a magnet in their I suspect it will come out covered in bits.

 

Rust never sleeps, so if it is in there it will continue to rust and flake off, until a hole forms.

 

If you do plan on having it cleaned at a later date, you have a few options as a stop gap.

 

You can empty your tank via the drain hole, then filter the gas and run it through again and again until it comes out clean. Gas evaporates quickly and the nicer gases have some detergents in it so that should help get any free floating rust bits out. Benefit is you are only running fuel, so no problem when you fill it up again.

 

Alternatively you can drain the tank and run evapo rust/water mixture. The only problem is unless you have money to spend on a large amount, you will only be able to coat the bottom even in the diluted form. I've thrown in bolts that I considered garbage in a bucket of the stuff, and they came out clean. The only fault with this is that it did leave behind a residue, which would be very difficult to vacate without being able to shake the tank with soap etc. There are some other treatments on the market which essentially coat the inside of your tank sealing the rust bits onto the tank (think glue). This works, but some people have reported that they had black residue clog up their filters with subsequent fill ups, the worst story I read was some guy had his fuel lines clogged from the paint (not long enough dry time).

 

Finally you can just run multiple fuel lines and filters. Once 1 fuel filter clogs up, swap to the next one with the filter, repeat until no more sediment comes through the line. Hard to paint a picture but think about it like a ringed circuit.

So you have two lines coming out of the tank (split the line via a tee), then you have a side of the tee go to a valve and filter and the other side go to a bit of hose with a valve on it. Both of these lines T back to 1 line. Split and repeat. Essentially, you close the valve on a filter line when it clogs, and open one of the non-filtered lines as the filter clogs. With 3 circuits you can get 3 filters full of crud before you will have to take it apart. Alternatively you can run several filters in line and carry barbs and bits of hose in your car to pull the filter and bypass them as they get clogged.

 

Quite a bit of work involved in this one, at which point dropping a tank and rinsing it out seems like a much easier solution.

 

Honestly I would find a friend with a garage where you can drop the tank. Make sure you have replacement hoses if any seem cracked or you don't think they will be able to be removed without cracking. Take the tank off and throw in some small washed rocks and tumble it.

 

I do understand that this may be difficult, not everyone has space or tools, so if that is the situation, I would run the gas through the tank a few times as described above and then install a few filters inline and keep bits of hoses and barbs to remove clogged filters. If you can get a majority of it out and keep your tank full so no rust can form (rust needs oxygen) then the sediment that comes out will be the larger bits that weren't able to fit through the drain hole disintegrating over time. That should be more then fine as far as stop gaps go.

Edited May 5, 2014 by seattlejester

[Italian]

That is exactly what I was looking for, thanks!!

 

I'm going to do the draining and filtering method one of these weekends as its the most feasible in my situation. I talked with a friend of mine about this last night and the plan is to get a few cheap five gallon buckets, barb fittings, some hose, a simple on/off valve, and a 100 micron mesh filter sock, then set up the whole operation to run in a day. 

 

Might do the multiple filters thing, but I'm not sure at the moment. I'll keep thinking about it for sure though.

 

On JNC I got a suggestion of washing the tank and lines out with mineral spirits, which I think I might do to just the hard line running from the pump to the engine bay as I'm sure they're fairly rusty and gunky. I'm gathering parts to re-do all the fuel lines this, so their condition will soon be irrelevant. 

 

 

 

So the current plan:

 

1. Wash out tank while I'm at school to get all the current sediment out.

2. Drop the tank once I get home and have it professionally cleaned and treated. Might have a sump welded on, at the least I want AN bungs welded on in place of the barbs for out/return (if this is possible at least).

3. Replace all fuel lines with braided hose and AN fittings. 

[seattlejester]

Sounds like a good plan, honestly I was thinking like a couple of used T shirts/cloth just to catch the sediment. The most practical would be to make sure you have less then 5 gallons in the tank, drain into a 5 gallon jug, pour that jug into a new jug via a filtered funnel (funnel/t-shirt/funnel sandwich). That should catch any major sediment without having to wait to try and flush it through a tiny filter.

 

Just be sure to be careful, you are dealing with large volumes of gas, and it only takes a curious person walking by with a cigarette to turn the whole operation into a big fiasco.

[Xnke]

Slushing the tank is kind of hit and miss nowadays...a LOT of the old standby, and some of the newer systems, of tanke slush don't hold up to the alcohols in fuels, and they turn to a sludge and/or loose adhesion and peel out of the inside. Make sure you get one rated for alcohol and gasoline!

 

Not even the old "Red Cap" sealer holds up to alcohol mixed fuels, as it's designed for aircraft...which IIRC aren't allowed alcohol in the fuel!

[Italian]

Seattlejester, thats a great idea, cheaper too. Just find a shirt large enough and tie/bungee cord it around the bucket to pour fuel into, then have hose and a valve at the bottom of that bucket to drain the clean fuel back into the tank/gerry can.

 

Yes I'll definitely be thinking of that. Luckily theres no smoking at school (its a boarding school, against the rules) and neither of my friends smoke so their garages would be okay as well. Question though, would it be safe to use an electric fan to ventilate a garage of the fumes? or would I have to worry about arcing in the motor possibly igniting the fumes?

 

 

Xnke, thanks for the tip! I have a good bit of time to research whether that would still be feasible or if a fuel cell of some sort would be a better option, so I should be able to figure something out.

[seattlejester]

Yea the new ethanols can really play havoc with any treatment system. That's why I am a bigger fan of acid treating and keeping the tank full, granted I moved to a fuel cell. It can be quite a bit of work though and you get a whole new slew of problems switching ton one, so my advice would be to stay away unless it is needed.

 

As long as the wires are sealed and you don't plug or unplug it it should be fine. Static is probably a bigger factor then some fan arcing all of a sudden. Just be mindful and you will be fine. Make sure and post pics, I'm curious what will come out of your tank.

Edited May 7, 2014 by seattlejester

[Italian]

I did some searching around last night and I think I'm going to go with a custom tank like in this thread: 

 

http://forums.hybridz.org/topic/96955-a-%E2%80%9Cstock%E2%80%9D-fuel-tank-solution/

 

Benefit of a new Al tank that wont rust, with welded in bungs and such, but without the issue of a fuel cell it seems.

 

 

Awesome. It looks like I'm going to be doing this at school in a big parking lot, so it shouldn't be an issue. I'll definitely be taking pics of the process and what comes out, it should be pretty neat.

[Italian]

Sorry it's been a while, I've been busy with the end of school.

 

I drained the tank and filtered everything on Sunday.

 

 

I expected nasty, red gasoline to come out, but that was no the case at all.

 

Here are the buckets in order of when they were filled. First bucket was the first to gas, ect.

 

 

 

 

As you can see, there was a considerable amount of gunk that came out initially, then a little more in the second bucket, and barely any at all in the third. Once I filtered all of that I put it back in and repeated the draining and filtering, and no more sediment came out.

 

I also cleaned the pre-pump filter, but I forgot to get picture. It was full of really thick gunk that I had to clean off the glass with my finger as running water didn't get it off at all.

 

 

I haven't started or driven the car yet, but I will tomorrow, so hopefully all is good. I'll update here with whatever happens.

[seattlejester]

Surprisingly that's not as bad as I thought it would be, but that amount is definitely enough to cause problems in a small fuel line/filter.

 

Hopefully that does it for you. Only option after this is the fuel lines and the pickup. Good luck!

[Italian]

I drove it this weekend and the problem persisted. I cleaned the fuel filter again as a little more rust make it back in, which signifies that the fuel puck up is the cause of it. Only a little came out, though, so it shouldn't be too big of a deal.

 

I did figure out that the fuel pressure regulator is bust, which is why there was never fuel pressure. My friend's dad suggested clamping the return hose to see if it builds pressure, which it did, and what do you know, fuel pressure. I ordered a Holly pressure regulator to hopefully fix thisand get me home (http://www.jegs.com/i/Holley/510/12-804/10002/-1?parentProductId=#moreDetails). Once I do though, I plan to replace it with a Fuel Lab 525 regulator so that I have a return system. 

 

I have a quick question on the regulator though. I plan to use only one of the two outlet ports on the regulator to avoid cluttering up my engine bay, would this cause any flow issues? I've already ordered the fittings and a plug, so now is kind of a bad to to ask, but I can always get another fitting somehow.

 

Thanks

Edited May 26, 2014 by Italian