fairly new member 76z low fuel pressure ?

[racebird1]

Hope someone can help. I am pretty new to the fourm but have spent a ton of time researching here and the fsm and FI Bible to find some information to help solve my problem. I will tell you what I know and maybe someone can tell me what I don't. I have a 76 z been sitting for 18 years. I got it started but is a bit hard to start. I cannot give it gas or it just breaks up very bad and backfires through the intake. If I give it gas very slowly it will rev up pretty good(very slowly). I have drained fuel tank and put in good gas. I have installed a new battery. I have tried to swap out ECU brain and no change. I have checked and fixed all vaccum leaks. I have isolated sections of vaccum lines and pulled vacum and it holds. Yesterday I pulled fuel pump because it doesn't seem to be getting much fuel and found very clogged strainer. I also have a extra pump and found the same. I noticed that both pumps were not put together the same. The center disc with the offset hole for the pump rollers were not in the same way.I can also tell someone has been there before. The pump the was on the car had 2 rollers stuck in place with lacqure and varnish. I am not 100% sure which way to put the disc but tried several ways and on bench testing only got 10 lbs on 1 and so far none on the other. How many psi with gauge from hose right to pump. Continued

[racebird1]

I lost what I just added so I will try again. The fuel pump has a alignment line on it that I am sure it's location is very important. Does anybody have a pump lying around that they could look at and see where this line is supposed to be lined up at. I found no reference to it anywhere and can find no match marks on the rest of the pump. I am using a regular pressure gauge to try to test pressure. The one I bought only went up to 15 psi so I am trying this one that is 0 to 160. I also put a hose from the outlet of the filter directly into thr gauge and still only get 10 psi. I do thingk that there is decent flow. I then took the return line off right by the filter and started the engine and I don't get any fuel going back to the tank. It actually looked dry inside that line. Shouldn't I be getting a little fuel returning? I checked the timing and it is high at idle it's about 25 deg. and if I take it back to 8 deg it will stall. The PO has tried to get this running and may have done some things wrong and has given up and I mean permanatley (meaning he is now pushing up daisys). If my pump is bad where can I get another one I have not seen one on e-bay. Thanks so much for any help you can give I would really appreaciate it. Anywhere I can help in the future I would be glad to.

[DatsunZsRule]

"been sitting for 18 years. I got it started but is a bit hard to start. I cannot give it gas or it just breaks up very bad and backfires through the intake. If I give it gas very slowly it will rev up pretty good(very slowly). I have drained fuel tank and put in good gas."

If it sat for 18 yrs. you will need to do more than just simply draining out the old gas and refilling with new gas. The inside of that tank I'll bet you has all kinds of crud and rust inside. This "Crap" inside the tank will just continue to break up and clog lines and the fuel filter which will result in low fuel pressure and cause an issue like your having. The Fuel injected 280Z's should be maintaing 36.3 PSI @ idle.

First thing I'd do is remove that gas tank and get it cleaned INSIDE thoroughly.

[racebird1]

The FSM says the system will maintain 36.3 psi above the vaccum. Should my pump be putting out at least 36.3 psi and I definately agree that the tank must get cleaned but right now I am getting clean gas out and I just want to get this thing running good before tearing it completely down. Will low pressure cause it to run like that? Thanks

[DatsunZsRule]

The L Jetronic uses a Roller vane pump. The roller cell is driven by an electric motor at over 3,500 RPM. This pump is capable of pressure in excess of 100 PSI which is far higher than any engine or F.I. system require. This is why this type of pump is located very close to or even inside the fuel tank because it does such an excellent job at pushing the fuel.

Yes, low fuel pressure will cause symptoms like your having. The cause of low pressure can be more than one thing. Like a minor fuel leak somewhere in the system, clogged fuel filter, clogged or kinked fuel line ect., or yes a defective fuel pump BUT more often than not a defective fuel pump usually bypasses the "poor running" stage and simply stops operating.

My opinion is this- until your fuel tank gets removed and cleaned very good internally, you will continue to have issues due to all the crud inside. A fuel tank can not be pretty inside on a car that has sat 18 years. Ifyour looking at getting it to run good as your first priority then I still recommend what I wrote above and get your fuel tank cleaned. The fuel may look clean to you coming out but I'm sure there is some small particles of junk that you cant even see. The fuel filters on the 280Z's are capable of filtering particles as small as 10 microns. This level of filtration is necessary due to the very small opening at the tip of the injector so as you can see, you can't always go by "The fuel LOOKED clean coming out

Best of luck,

[racebird1]

This problem for the most part has been solved today. What I realy needed to know was how the fuel pump is supposed to be assembled. The Po had it apart and aparently put it back together wrong. I toyed with it for awhile today and through process of elimation I got it back together properly and it now pumps over 50 psi I put it back on the car and she now revs up perfectly I was even able to drive it a bit. What a good feeling to drive a 280Z thats been dead for 18 years. For anybody that needs to know when taking the pump apart make sure you carefullY match mark all the pump head pieces. Looking at it straight on from the suction end and the discharge outlet nipple pointing up, the suction nipple will be a 3 o:clock as shown in the manual and the center pump disc should have a match line or possibly a grove and that mark should be at the 9 o:clock position. It pretty much lines up with the notch in the pump housing. It is also possible to put it in upside down and then it won't line up correctly. Also remember the the inlet filter screen clogs easily an is most likely going to be a major csause of low fuel pressure. It you z breaks up when you give it gas check you pressure and if low check this screen if it's got dirt in it you will need to clean your tank as previously stated. This z would bearly start or run on 10 psi of fuel. Got the pressure up and it runs pretty darn good for sitting 18 years. Now I know it runs and can start with the restoration and know I will end up with a running car.

[zbane]

Jumping in a little late here, but I think this will help you in the future.

This is a link to atlanticz.ca

They have a great reference area, well written, nice photos. I think that taking information and insight from our site and combining it with the visuals provided at the other site is a great benefit.

I hope this will help

http://www.atlanticz.ca/zclub/techtips/EFI&fuel.htm

Welcome to the club

[sblake01]

What's your fuel pressure when you check it under the hood at the fuel filter outlet? You should be looking for ~36.3psi there.

[racebird1]

I checked the pressure today under the hood with a tee fitting just after the filter and got almost exactly 36.3 psi. It held the pressure for a few minutes but very slowly started to bleed down a little. I left it hooked up to the gauge to see what I have tomarrow. How long should it hold pressure? I also checked the return line and I have plenty of gas now returning back to the tank. I am going to run a line to a temporary tank tomarrow so I don't suck up crud from the old tank. It still ran a little ruff today because of the cold I got to looking into the dist. and found that it is not advancing. I have it out and I am cleaning it up. The grease between the rotation plates is all dried up and just needed cleaning. There is no rust what so ever but does anybody have any suggestions on what type of grease to use in there?

[sblake01]

I checked the pressure today under the hood with a tee fitting just after the filter and got almost exactly 36.3 psi. It held the pressure for a few minutes but very slowly started to bleed down a little.

How much is a little? Could be a bad check valve but if it holds enough pressure to start up right away each time, assuming that your cold start valve/thermotime switch are okay, I wouldn't worry about it.

[racebird1]

When I checked this morning thats about 20 hours after shutting it off it still had 11 psi pressure on the gauge. I may have to do additional tests to see if it is leaking out a injector or the check valve. The distributor is back in and running. It does seem to be burning rich untill it warms up, Then it runs almost perfect. The vaccum advance works very well no hanging up or sticking. I would suggest that if anybody takes one appart to take pictures and mark things as you go. There are a lot of pieces and could very easily be put back together wrong But it is doable.