Bosch 044 fuel issues

[2eighTZ4me]

Thought the reason I was burning up fuses was b/c of the 10 micron filter PRE pump. Swapped that out to an Aeromotive 100 micron filter and a -10AN line from the filter to the pump (up from a -8AN). Problem got better....BUT....after sitting in a lot of stop and go traffic - the pump died. Once it gets hot after about an hour of driving - the pump starts to get loud. On cool mornings - I can't even hear the thing on the way to work - which is an hour drive each way. On the way home is a different story. Pump starts humming after about 45min. into the afternoon commute.

 

On two occasions when it has died - I pulled the fuse and one side of the plastic was burnt. Fuse didn't blow - but it damn sure got hot. Replaced the fuse - and it fired right back up and got me home. Tested the fuse when I got home - it's still good.

 

I am using the STOCK wiring for the fuel pump. I spliced into it under the dash. I'm guessing I need to run a straight 12GA wire from the relay board to the pump to drop resistance?

 

Pump is mounted in the stock location. I know I'm missing some details - but that's the gist of it. Car/fuel gets hot, pump gets loud and just shuts down for a while. Not sure if replacing the fuse did any good - or whether the cooling down did the trick.

 

I'm either looking at going to -10AN from the tank to the pre-filter, or straight wiring 12GA. from the relay board to the pump. I'd like to be as minimally invasive as possible - but just want to see if anyone else is running the 044 pump and has had any heat relate cutoff issues.

 

Thanks in advance...

[Nigel]

That pump pulls around 10A, and the stock wire is what... 18AWG, which is good for maybe 5A max. So, yes to running 12AWG wire to the pump. Also, you may need to lower the pump. Hi pressure pumps don't like to pull fuel and will run harder to do so. What's your fuel tank setup?

 

Nigel

[seattlejester]

Hmm are you clogging the filter? Fuel cell or original tank?

 

Genuine curiosity. I have a bosch 044 unit as well, would hate to hear that they are unreliable. Mine's running a 20 amp fuse and I think 14 gauge wiring. It's never been on for more than a few minutes though. Only time it gets loud is on initial pickup, once it's pushing fuel it seems happy.

Edited May 8, 2014 by seattlejester

[AkRev]

Few things. 

First, 18 gauge wire is not the problem. If it was, they would not use that small of wire to wire cars from the factory.  

Second, Followup questions;

How old is the pump? How many hours have you ran the pump? how is the condition of the return line?

 

Things to think about, if you are using stock wires, these are now very old and brittle. Movement will ruin copper strands inside the wire and will make 18 gauge wire to act like a much smaller wire. Side effect of this would be heat in the wire. 

 

You noted that your car shut off in stop and go traffic, I have experience with killing a good fuel pump because my return line was too small (or clogged). This will cause the pump to work harder and create extra heat.

[2eighTZ4me]

Return line is the factory hard line. Pump (and car) has 2043 miles on it. Brand spanking new. Fuel comes from the dead bottom right of the FACTORY tank. I mounted a -8AN 3/8" 90 degree fitting in the bottom of the tank where the drain plug is. The old 10 micron pre pump filter has been replaced with a brand new 100 micron filter less than 400 miles ago. The tank was boiled and sealed. There is no sh** being sucked up. The pump is mounted in the stock location. Pretty much dead even with the outlet on the bottom of the tank....maybe a wee bit higher.

 

The problem is clearly heat related - and related to the heat of the fuel, as it gets hotter and hotter being pumped through the system. The pump is lubricated and cooled by the fuel - and when the fuel gets hot - there's a problem.

 

Here's the deal. Everything I've read stated that the 044 pump is to be used inline with a feeder pump. I can see that making it the only pump would make it upset a bit.

 

I don't want to replace it, but if I have to go with a 'single' pump - like an Aeromotive A1000 - and wire it with 12GA. - I will. Don't really want to go with a -10AN outlet out of the tank - that'd be a freakin' fuel mess...but I will do the 12GA wire directly first - that seems to be the sentiment echoing here

. It's burning up the fuses on the MS relay board - so I have to think that excessive amperage is being pulled by the pump under hot conditions - causing the fuse to fail due to the pump trying to pull too hard on hot fuel...

 

This is a turbo car with no hood vents (Carbon fiber hood) and gets dogged pretty hard daily with 16 intercooled psi. Air intake is underhood above the factory AC compressor. I know IAT's are probably a little hot -- not helping the situation any - but it is what it is....

 

And Nigel - many thanks to you for the 240SX tranny swap writeup!! I have one in this car, and in my racecar - and I have been completely pleased with the performance of them! Followed your Motortopia writeup to a T - worked like a champ!!

[NewZed]

 

The problem is clearly heat related - and related to the heat of the fuel, as it gets hotter and hotter being pumped through the system. The pump is lubricated and cooled by the fuel - and when the fuel gets hot - there's a problem.

 

- so I have to think that excessive amperage is being pulled by the pump under hot conditions - causing the fuse to fail due to the pump trying to pull too hard on hot fuel...

 

I'm not sure this logic works.  There's a lot of fuel available for cooling, if it's flowing.  Why don't you get rid of the pre-filters for a while and see what happens.  Or at least confirm that the flow rate of the filter matches the flow rate of the pump.  100 micron particles probably require a pretty large surface area to allow a high flow rate.  "100 microns" doesn't tell enough.

 

Also not clear on how a hot pump draws more current, causing the fuse to blow.  A non- or slow-spinning DC motor draws more current, I believe from my limited electrical knowledge.  But a hot motor, maybe not so much.

Edited May 8, 2014 by NewZed

[Nigel]

Few things. 

First, 18 gauge wire is not the problem. If it was, they would not use that small of wire to wire cars from the factory.  

 

 

There's probably 10+ feet of wire to the pump, and it's bundled with other wires, so 18AWG is marginal in that situation already. The factory pump was a low pressure feeder pump that likely only drew a few amps. Yes, 12AWG is overkill, but it's better than being undersized.

 

 

The problem is clearly heat related - and related to the heat of the fuel, as it gets hotter and hotter being pumped through the system. The pump is lubricated and cooled by the fuel - and when the fuel gets hot - there's a problem.

 hard daily with 16 intercooled psi. Air intake is underhood above the factory AC compressor. I know IAT's are probably a little hot -- not helping the situation any - but it is what it is....

 

And Nigel - many thanks to you for the 240SX tranny swap writeup!! I have one in this car, and in my racecar - and I have been completely pleased with the performance of them! Followed your Motortopia writeup to a T - worked like a champ!!

 

How much fuel is in the tank when this happens? When the volume gets low, with a high output pump like that, you're recirculating the entire tank volume in a matter of minutes. As you mentioned, the fuel picks up heat from the engine bay with each circulation and gets hotter and hotter. I've installed a fuel pump speed controller in my Z to vary the pump speed based on demand (Professional Products Fuel on Demand, but I think it may have been discontinued).

 

Glad to hear the SX swap worked out for you!

 

Nigel

Edited May 8, 2014 by Nigel

[2eighTZ4me]

When it first did it with the 10micron filter pre pump - the tank was fairly low. This time, however, I had nearly 3/4 of a tank. It was 86 degrees out yesterday and traffic sucked! Sucked even worse when the car died in it!! I have been conversing with the DIY AutoTune folks and I'm going to run a few tests tonight - namely a current draw across the fuse on the relay board that keeps getting smoked.

 

I am convinced that running a single 12GA wire from the MS relay board straight back to the pump could not hurt anything. And it will give me peace of mind that at least that piece is out of the equation. I'll go after removing the pre filter next if this doesn't work

 

I will also be replacing the entire MS relay board over the weekend. The one in the car now was bought off this site and have no history on it. Plus - the fuel pump fuse socket is nearly wasted from all the heat and pulling of fuses...

 

Thanks for your help guys!

[johnc]

If possible, mount the pump lower then the fuel tank so you get a siphon going. Testing the current draw is a great idea. I ran that exact pump on my race car and used 14ga wire with a 15 amp fuse. Shield the pump from the exhaust if it's close.

 

With today's Ethanol diluted fuel it has less "cooling capacity" then when that pump was originally designed.

[AkRev]

Not trying to start a pissing match. Just trying to help the OP.

But to add to my case, my car burned and forced me to rewire the whole car from scratch. I run the same 044 pump, with 18 gauge wire, with a pre-filter, on a longer 2+2, and ran it in Houston, Texas with no problems. 

 

I am not saying that his wire is not the problem, just the fact that it is 18 gauge does not mean you should point to that as its only problem. Old wire is more of a suspect than the size.

 

Please note, these pumps do fail if mounted vertically, and do not like to be mounted higher than the bottom of the gas tank, as Johnc pointed out.

 

Still, the one thing that sticks out to me is the problem with stop and go traffic. I understand that it could be a lack of air movement that could cool the pump, but there is a part of me that still wonders about the condition of the pressure regulator and return line.

 

Have you tested line pressure?

Edited May 8, 2014 by AkRev

[2eighTZ4me]

My pump is mounted horizontally in the exact same spot/position that the stock (1978 EFI) pump was. It even fit right in to the stock mounting bracket. No need to reinvent the wheel. If it was good enough for the Nissan design team for mass production - I have to think that it would be sufficient in my case as well. It's not close to anything hot. Unless the diff heats up in stop and go traffic

 

I have an inline pressure gauge (and an Aeromotive pressure regulator) and it reads 40psi spot on all the time (except when it dies!) Again - the car has roughly 2100 miles on it now - the parts are still pretty much brand new. The pressure gauge is plumbed in just before the fuel rail.

 

Being that I pull fuel from (what used to be) the tank drain plug - it's nearly impossible for me to mount the pump lower than the tank, which is why I try to always keep at least 1/2 tank in it at all times.

 

I have a sneaky suspicion that excessive underhood temps, coupled with minimal ventilation, are heating the fuel up - even though I have taken great care to route the lines as far away from anything hot in the engine bay as possible. I am running a -6AN line all the way from the pump outlet to the front of the car as well.

 

I tried to look up the flow rate of the pre-pump filter with no luck. Filter is an Aeromotive 12304.

 

Just throwing out as much info as I can to you guys....

[NewZed]

Don't forget that the fuse is just a thermal overload device.  Heat from other sources can push them over the edge.  Maybe your relay board is in a hot spot.

 

The pump motor failing from overheating is not the same as the fuse blowing from excess current and overheating.  If the fuse was sitting next to the pump where heat could be conducted through the wire to the fuse that would make some sense but the relay board is probably 12 feet away from the pump.  It doesn't see any pump heat. 

 

 

You said that you have the stock tank with stock return lines but the only car in your sig with MS is a 73, which has the small return lines.  Probably not the specific issue though, since if you had back pressure at the return line your fuel pressure would be uncontrollably high.

 

 

Edit - the older 240Z fuses were known to blow and/or melt their surroundings due to poor contact at the fuse, allowing corrosion and a high resistance connection.  It's resistance at the fuse area that produces the heat that blows the fuse.  Increased resistance at the pump lowers overall current draw and saves the fuse.  If pump motor resistance drops when it gets hot that could cause excess current through the fuse.  Focusing on heat is right, but the general "heat is bad anywhere" view isn't going to get you there.

Edited May 8, 2014 by NewZed

[AkRev]

Based on that, I would replace the wire to the pump. That is about the cheapest most effective thing you can do at this point. (unless your fuel pump is under warranty) 

Please, make sure you also replace the ground wire as well.

[2eighTZ4me]

My relay board is mounted in the engine bay right next to the clutch master cylinder - where the dropping resistors used to be. Just to be clear - I'm using MegaSquirt relay board to power my fuel pump. It is where the fuse and pump relay live. I bypassed ALL the stock 1978 wiring - save for the one that goes back to the pump. Spliced it in to the relay board.

 

NewZed - yeah - I need to update my signature file. My 73 has a fuel cell and nothing stock about it. This is my 78 that I'm trying to make a DD. You did have a great point about the fuse socket though....mine looks pretty trashed as mentioned before, so maybe the fuse is heating up there from a bad connection....Good call!

 

This weekend, I will replace the relay board AND the wire going from it back to the pump....providing Mother Nature doesn't dump rain on me all weekend...

[2eighTZ4me]

Well - ok. A little testing/wiggling revealed that indeed my MS relay board has bad posts for the fuse. As I'm trying to get a reading - and jiggling the fuse in the process, I can see sparks in the fuse holder, while listening to the pump turn on and off. Fuse was hotter than a firecracker after about a minute of the pump being on (and off and on and off etc.... Long enough to hook up the meter....and have a swig of beer......

 

I'll be replacing the relay board and a 12ga wire to the pump before I even bother you guys again. This has GOT to be it...bad fuse connection as NewZed stated - causing my fuses to burn up....before they blow...... due to crappy contact.

 

Could also be the cause of my intermittent miss when I go over bumps..... a two-fer would be nice.....I don't get many of those....

[Sean 83ZXT]

... Fuel comes from the dead bottom right of the FACTORY tank. I mounted a -8AN 3/8" 90 degree fitting in the bottom of the tank where the drain plug is...

 

It sounds like you may have found the source of the issue but I noticed the line above. You don't state whether the fitting is a tube or cross drilled but I vaguely remember reading a tech article by Aeromotive stating that cross drilled fittings are restrictive and can cause pump cavitation. Could be another thing to look at.

[2eighTZ4me]

Here's how it's fed. The fitting maybe sticks up 1/3" inside the tank.

 

[DuoWing]

I've been going around anytime I see a thread like this in order to tell people that the stock wiring is in fact too small for a larger pump like the Bosch 044. I was running into the same issues. I swapped in my turbo harness and used the factory turbo relay with the original 76' 280z wiring for my fuel pump. After running for a bit the pump would always get loud, I'd get some bogging, and my pressure would drop. The relay would get pretty hot. I started testing. When completely cold I was losing little to no voltage from the pin coming out of the relay to the terminal on the pump. After running and getting warmed up once the relay started becoming hot and pressure had dropped I tested the pin going into the relay connector and coming out. I would see maybe a .1~.2v max drop. The real issue was the wire coming out of the relay, I was seeing a full 1v drop between the wire coming out of the relay and the positive terminal on the pump. That's a long distance to travel. All you have to do is look at the Bosch 044 vs the stock pump to know that it's going to require more power. It's nearly double the size. Finally I switched to a larger 50amp relay which would still get warm and completely rewired my pump to come directly from my maxifuse blocks and go straight to the pump using 10 gauge wire. Now I've since upgraded to an even larger 70amp relay, the kind you get with those electric fan kits. I've since tested the pump wire coming out of the relay and at the pump and now I lose only .3v. I also still use the stock tank output and extended the factory mounting location so that my pump sits a little below the factory tank outlet. Now the pump seems to stay quiet and not have the issues it used to. On really hot days I may hear it a little, but nothing like before. A good while back I found a post on Z31Performance where jeffp was talking about the same exact thing and running into the same exact problem. He's the one who found that the stock wiring and stock relays were just insufficient to run a higher performance pump.

[skirkland1980]

The fuel is boiling before it gets to the pump. That is why it is loud. Some way to cool the fuel or an in tank pump would be about the only way to cure it.

[AkRev]

I am going to relate this to a recent experience that I had at my home. 

To me this is like me flushing the toilet at my house and when it backs up, I do not blame it on the pipe size. Yes, a small pipe will cause my toilet to back up, if it can not flow the water when I flush, it will not flush and it will overflow. Instead, I will get the snake and clean the blockage (in my recent case, it was a box of non disposable wipes that my youngest thought would be fun to flush down the toilet when no one was looking.)

 

Yes a small gauge wire will cause symptoms that have been described. But I trust the standards of AWG and Brown and Sharpe. To me I would believe that wires that have been exposed to almost half a century of heat cycles and then been forced around as someone replaces a pump are more likely to be the problem.

 

As I said before, cars are still produced with fuel pumps that use an 18 gauge wire (see Chevy and Nissan for examples.) A good quality wire well work great, I know. As I said before, I run that pump with an 18 gauge wire.