Fuel pump noise - too much?

[Daemione]

Hey everyone - I posted this question in the fuel delivery subforum several days ago, but haven't gotten any responses. Figured I'd try here, see if anyone had any input . . .

 

I've got a '79 280zx, and the fuel pump is awful noisy. For the month I've had the car, I just figured it was a normal symptom of it not being an in-tank pump, but I read something that makes me think that something might be wrong. Is the pump supposed to prime loudly for a few seconds & then stop if I don't start the car? Mine just hums loudly indefinitely until I turn the key off, or changes to a higher pitch if I start the car.

 

Anyway, here are some videos - the first one is from outside the car, about 8 feet away. I toggle the key from 'on' to 'acc' once, it's not shutting off on it's own. As far as I know, it will buzz like that indefinitely as long as I leave the key in 'on'. Mic doesn't pick it up as loud as it seems in person - it's the humming at a pitch of F#.

 

Second video is from sitting in the drivers seat, windows up. It's covered up some from the engine/exhaust noise, but when I start the car pitch raises to a G#. Again, the rear trim is missing, so it's probably a little louder inside because of that.

 

 

So any thoughts? Is it supposed to be running that loudly that long before starting? Should I be worried about the pump dying on me in the near future? Or is it all just normal noise as a result of an external pump?

 

Thanks in advance!

Edited November 20, 2010 by Daemione

[NewZed]

That sounds pretty noisy.

 

You should crawl up under the car, right where your first video is pointed and see what kind of pump you have and how it is mounted. You can probably squeeze up under there without even jacking the car up (parking brake on of course).

 

I've read that the Walbro 225s are pretty noisy. Or yours might be mounted with no sound deadening rubber mounting material. Ideally, the pump body and fittings are not contacting any metal, only rubber.

 

If your pump runs continuously with the key at On but the engine not running, then someone probably bypassed the safety switches.

[Daemione]

Excellent, thanks - weather permitting, I'll have the rear end up in the air tomorrow to replace some differential oil seals, so I'll get some pictures then.

[Daemione]

 

No markings that I can see as to what brand/model pump it is - there might be something covered up by a bracket, though. Rubber mounts are also all there, if a little dry. No obvious hacks/splices in the wiring either. Any ideas?

[rossman]

Pumps get noisy when the lines get partially clogged and they have to pump against a lot of back pressure. Check your fuel filter. Check fuel pressure. Blow out the fuel lines with compressed air.

[19762802+2]

http://www.atlanticz.ca/zclub/techtips/fuelpump/index.html

[Daemione]

Pumps get noisy when the lines get partially clogged and they have to pump against a lot of back pressure. Check your fuel filter. Check fuel pressure. Blow out the fuel lines with compressed air.

Good suggestions - thanks. I already have a spare fuel filter hanging around, but haven't put it in yet. Need to get a fuel pressure gauge, I suppose. Tomorrow's project is to replace all my brake pads & flush/bleed the fluid with new stuff. I've got all my tie rod ends & idler arm that need to go in, but if it's not too much of a hassle I should be able to get the new fuel filter in as a start.

[BLOZ UP]

Make sure the pre-pump lines and the inlet screen (if any) are clear.

[Daemione]

http://www.atlanticz.ca/zclub/techtips/fuelpump/index.html

Wow, lots of info there, thank you!

 

Here's what concerns me:

The fuel pump control for the 78 - 81 N/A.

 

When the engine is not running the oil pressure switch is closed and the transistor at the 'L' terminal of the alternator is "closed" and BOTH idiot lights for ALT and OIL are ON. When the key is turned to ON the idiot lights are on and the fuel pump is OFF. The fuel pump only "starts" when the key is turned to Start. These years used three relays to control the fuel pump. If the engine stops / stalls the loss of BOTH ALT and OIL signals simultaneously shuts off the fuel pump.

When my key is ON my fuel pump is most definitely on as well . . . which according to this is not correct. But on the other side, the FSM only mentions 2 fuel pump relays, not 3. And the fuel pump operation chart in my FSM (page EF-14) doesn't seem to have a listing for the ignition switch being on, but the car not started (so no oil pressure or alternator generation). So I haven't found in the FSM yet anything where it says definitively what the fuel pump should be doing with the car not running, but the ignition switch ON.

 

Electronics isn't my strong suit, but I guess I should test/replace the fuel pump control relays. Any suggestions on where to start?

[NewZed]

That looks like the stock pump too (maybe not original but factory issue) and they should be pretty quiet from what I've read.

 

That atlanticz link is a good one, read the whole page. Might help you get your safety system back working. The way you're set up now, if you bust a fuel line, your pump will just keep pumping gas. Not a good scenario.

[Daemione]

So the inlet filter screen . . . is it a sure thing that a '79 has one in the same place as the 280z? I didn't spot one on mine.

 

[NewZed]

That's not good. You might have been running rust particles through there for a while. Might explain the excess noise. If that was my pump, I would test pressure and flow then decide if it's worth keeping.

[Daemione]

Arg. Think it's worth taking off the top cap to take a look? It'd be a pain since the screws stripped out - I'd need to unmount the pump, and then clear it of all fuel traces so I can dremel slots in the screws to get them off. I'll probably just pick up another fuel pump. And also figure out what's up with the relay(s), if anything. :sigh:

 

Any chance another '79 owner could confirm their pump behavior with the key in the 'on' position? I'm still reading a lot of conflicting reports on what's normal.

[Daemione]

Oh, and for what it's worth, I put a new fuel filter on. It might be a little quieter now, but it also might be my imagination. I'm gonna try to take another video & compare that way.

 

I'm really curious as to how clogged the old filter was, though. If I were to cut open the old filter with a dremel, what are the chances of it turning into a little fireball?

[NewZed]

Page EF-8 in the FSM describes the fuel pump safeties. Alternator and oil pump switch.

 

Use vise-grips, pliers and a vise if you really want to see what's in your filter.

 

You really should check fuel pressure anyway, just as a typical maintenance check of pump, filter and lines (pressure drops), and fuel pressure regulator. Borrow a gauge if you can if you don't want to buy one.

 

You're not getting a lot of replies here, because this is 101 stuff, and you're on the grad level site. Download the manual and start reading, it's full of good things. The Engine Fuel section is the best.

[BLOZ UP]

My 77s fuel pump had no screen and it kept getting clogged. After I cleaned the tank and added a prepump filter, it was still noisy and couldn't flow enough at high load, specifically it would hit a wall at WOT around 4000; the pump was bad from inhaling rust for so long. I have a new pump now, some Summit cheapy that happens to flow more than the autozone stock replacement and it was cheaper, even after Summit's "free" shipping, and handling.

[Daemione]

You're not getting a lot of replies here, because this is 101 stuff, and you're on the grad level site. Download the manual and start reading, it's full of good things. The Engine Fuel section is the best.

Thanks for the page link re: fuel pump behavior - I somehow missed that in my read throughs. And I get that these aren't ground-breaking questions/issues - believe me, I'm doing my best to find these answers via search before posting. But finding s130 non-turbo specific information is a lot more difficult than S30's or turbo models. A lot of it is comparable - but it makes searching for the information I actually want a serious chore.

 

And there are a lot of little things I'm discovering that maybe people know about - but have never mentioned or documented. Like, for example, the speed bleeders BDA sells for the '79-83 are the wrong size, I found that out the hard way on Sunday. Another example - the energy suspension sway bar bushings are too thick. It's impossible to install them without shaving them down a decent amount first. I search high & low before buying things to be able to anticipate problems like this, and it's really discouraging to discover "new" issues on a 30+ year old car.

 

I have the downloaded version of the FSM, and I have a hardcopy as well. But I'm NOT confident in it . . . The FSM is unclear in many places, and downright WRONG in at least one section that I've found already (the heater controls - the FSM describes a linkage system for changing from floor/vent/defrost, when in fact the s130 uses vacuum diaphragms). I was going through it a couple days ago looking over a brake pad swap, and found 2 pages completely missing - in their place was 2 pages from the driveshaft section. Unbelievable. The digital version is better in that regard, but I go cross-eyed reading it.

 

Having become accustomed over the past 10 years to Helms manuals & their anal retentive attention to detail & extremely detailed diagrams, this FSM is a serious let-down. The Haynes that I have is slightly better in some regards, but has obviously cribbed a lot of it's info & pictures from the FSM.

 

Anyway, sorry for the mini-rant, I'm just frustrated a little at the amount of conflicting & unclear information out there about this car. In on-topic thread news, I found someone who's selling me the fuel pump relays (another inconsistency, btw - there are only 2, not the 3 that the atlanticz site says). So once I get them in, I'll do some testing to see if that's my fuel pump running problem. And when I get a few extra bucks, I suspect a new fuel pump would be a smart purchase - this is my daily driver, so I can't afford to have it give up the ghost with no warning. With possible damage done to it already, that's not a risk I want to take.

[Daemione]

Wanted to follow up on this - went ahead & swapped in a used fuel pump today from another ZX, and it made all the difference in the world. Shockingly quiet compared to the one that was in there (a remanufactured unit, according to a label hidden by the rubber mount). Also replaced some fuel lines under there that were pretty terrifying . . .