Fuel Pressure 26PSI

[chiefmd]

I've been steadly working on a 77 280z that I purchased over the winter. Just replaced the injectors and she is running quite well. I went ahead and installed a inline fuel pressure gauge and am only getting 26 psi. When I shut it off she holds pressure for a few hours but eventually drops off to zero, also, no problem starting up after its sits with zero pressure. I installed a Fram G3 filter before the pump and it is clean. I was going to clean the filter in the fuel pump but it's not OEM. It looks like the one that Black Dragon sells. Any suggestions as to what else could cause low FP. Thanks

Edited May 26, 2009 by chiefmd

[MEZZZ]

I am far from an expert but will give you my 2 cents. I beleive fuel pressure should be at 36.6 psi. I measured mine right past the fuel filter before going into the rail and came up with that exactly. Where do you have your inline guage? I am thinking it might be the fuel filter itself, (you dont state you replaced that) or the fuel pump might be gunked up.

Another thought might be the fuel pressure regulator at the bottom of the loop in the fuel rail...just my thoughts.

[DatsunZsRule]

Pressure should be at least 36.3 for a stock 280Z and it's suppose to hold at that pressure. If it fails to maintain that pressure while sitting then more than likely it's due to a bad check valve in the fuel pump.

[chiefmd]

Thanks for the input. Yes I changed out the fuel filter prior to installing the gauge which I mounted just after the fuel filter.

I checked it again today. Started right up. I let it run then shut it off and the fuel pressure bleed down to zero in 4 hours. So the fuel pressure should never bleed down?

Do all fuel pumps have a check valve in them? Could I put an inline check valve or just replace the pump? Can you recommend a pump and where to purchase. Also, would a bad fuel pump also lead to low pressure?

[DatsunZsRule]

Nope, Should not bleed down. If your certain there are no leaks anywhere in the system than it's more than likely the check valve.

Last time I checked they are not sold seperately so you have to replace with a new pump. For replacements they are still available new from Nissan so check with your local Nissan Dealer first. If they can't help you out (Like my local dealer ) than go try Courtesy Nissan www.courtesyparts.com if you can't locate one on there site, try shooting them an e-mail or call them up and ask. It's one of those parts where I highly recommend replacing with a stock genuine Nissan but thats just my opinion.

[DatsunZsRule]

OK Correction, you can get just the check valve only. Z Car Source has them for $48.44 but still call and shop around. ;)

Here is a photo of it I stole from Stephen

[chiefmd]

The car came with an aftermarket fuel pump so I don't think I can change out the check valve. Looks like I'll try for an OEM one. Do you happen to know the part # for a 77 280Z pump?

[DatsunZsRule]

I had a Parts CD I got from Courtesy Nissan a long time ago and can't find the damn thing (I Know guys, Should have gotten it from here )

I'll keep looking but someone here thats got the Club Parts CD will hopefully chime in here.

[chiefmd]

Really appreciate all your help. Thanks

[DatsunZsRule]

Thats what we are all on here for Let us know how everything turns out.

Edited May 27, 2009 by DatsunZsRule

[TomoHawk]

www.Rockauto.com is a good source for parts like the fuel pump. They will list all kinds of stuff for the Z.

[bobs77]

I replaced the check valve in my stock pump ('77 280Z) and it still bleeds down. Fuel pressure is a little low at 32psi, not 36.3. It runs well most of the time, except on warm days when I try to re-start it after driving for a while. When it starts the idle speed is only ~600 and it runs rough. I have to bring the idle up to ~2000 for 10-15 seconds and then it's fine. I tested the regulator per the FSM and it passes, and there are no visible leaks anywhere so is this a sign the pump is showing it's age?