Fuel pressure

[bhermes]

A quick update. I have been having issues with my 76 280z leaving me stranded on the road about once a week. I suspected that I may have rust in my gas tank causing the issue. Initially confirmed by seeing brown specs in my fuel filter and confirmed after dropping my tank. I cleaned and re-coated my tank with red-Kote and re-installed. I replaced the fuel filter but did not replace my fuel pump. It was recently replaced and thought I may be able to save it. I hooked up a gauge after the filter and reading about 28psi pressure at idle and pretty consistent when I rev the engine. Also checked in gear but not yet during actual driving.

I know there are a few posts but bare with me, again not a mechanic.

Does the value sound correct. I have read posts about 36 psi and gauge pressure vs atmospheric pressure and so on.

Can I assume with this reading that my fuel pump is acting properly.

Thanks in advance. Trying to get ready for new paint job in a couple months but want to make sure the car is mechanically sound.

[Wade Nelson]

Carry a can of starting fluid with you. Next time it dies give it a spritz and see if it will start. First thing you've got to do is CONFIRM whether the problem is fuel or ignition related.

[bhermes]

This may be a dumb question, ok questions can not be dumb but the person asking may be. Where should I spray the starting fluid?

Does 28 psi sound correct or is it not that telling?

[FastWoman]

Yes, 28 or 29 sounds fairly correct, depending on how you're measuring it. A much better way to measure it would be to pull off the little vacuum hose that goes to the fuel pressure regulator. When you do that, the fuel pressure should jump up to 36.3 (?) psi. The lower reading with the vacuum hose connected really depends on the vacuum reading. It might be correct, or it might not. You would really have to give us both readings. However, 36.3 with the hose disconnected (and hence zero vacuum) would confirm your pressure is right.

Is your car still quitting on you, even after cleaning and coating the tank? If so, Wade is offering you some good advice.

Where to spray the stuff? Well, an EFI engine is a bit tricky in that regard. You want to spray into the intake. I've sometimes done that by removing a vacuum hose from the intake manifold and spraying directly into the fitting. Pretty much any convenient orifice in the intake system will do.

[bhermes]

Ok, I will check the other reading and carry starting fluid. Long story short about 30 days ago I drove the car from one house to another about 10 miles and the car wanted to die a few times or appeared to be struggling for gas. Did make it home. I was suspecting fuel pump issues but without going into long detail the car might have just been low on gas (should of had 4-5 gallons but I think someone was running the car daily for about 60 days prior to me getting the car back - a friend, cant really blame them). The car has sat for about 30 days and had trouble starting. I added about 1/2 gallon of gas and the car did start. I have since added 5 gallons and drove the car around the block with no issues. I was hoping for a little better weather before going for a long drive. I hope to get out a little more this weekend. The other possible problem may be a hole in the pickup line. I think I will see how much gas it takes to fill up and see how low I may have been.

Thanks and I will reply in a few days.

[FastWoman]

"hole in the pickup line"

Yeah, that happens too! It happened on my '75 when the car was only 8 years old. It would only empty to a half tank and then draw air.

[bhermes]

I guess I will fill up the tank this weekend. Then drive until empty or until it breaks down. What a shame, a weekend of driving the z.

Has anyone had the hole in the pick up line and actually repaired the tank or is this a basic tank replacement at that point. I guess the cart before the horse but just preparing for the worst.

Car sat empty for close to 15 years which is probably common for some of the cars out there. Plenty of rust in the tank when I dropped it.

Wish me luck and if the car breaks down hopefully somewhere interesting.

[FastWoman]

I had mine fixed, but it was so long ago I can't remember what was involved or how much it cost.

[bhermes]

Well it is beginning to look like a case of someone driving or at least running my car behind my back. I put 2.6 gallons into the car and drove around the block (1 mile) with no issues. Added another 2.6 gallons and drove around the block twice (2 miles) no problem. You get the picture. Did this at 2.6 gallon intervals approximately and have added a total of 16 gallons with the car running fine each time. If I am correct the car holds about 17 gallons so the car was more than likely empty. I will finish filling the car. I will not feel completely good until I run through one tank of gas but so far so good. Also, prior to dropping my tank the fuel gauge did not work. It appears to be working now. I cleaned the fuel sending unit pretty well when I had the tank down.

I am guessing now, and only a guess, I have a vacuum leak. I will do the test and confirm. No need to get into this until I check.

[FastWoman]

Well it is beginning to look like a case of someone driving or at least running my car behind my back.

Gremlins!

FAIW, I once had a car with disappearing gas -- a '71 Plymouth. I thought someone was siphoning it, but in fact it was a pinhole leak in the bottom of the tank, apparently created by a flying rock.

Edited March 17, 2013 by FastWoman

[bhermes]

Well it appears that I do have a small leak somewhere. Hopefully a fuel line that I did not get back on correctly. But if tank has a small hole looking for some help on if there is something I can coat the outside of the tank with to possibly seal off. Not really in the mood for purchasing a new tank yet. Used Red-Kote on the inside of the tank.

Trying to get a 2000 Ford Taures, with some sort of enginer issue, out of my garage so I can work on the Datsun while it is raining and 30 degrees out. Will check when weather clears.

[Zed Head]

I had a pinhole leak on the bottom of my Pathfinder tank (a manufacturing flaw I assume since I bought it new). I used a two part epoxy designed to seal gas tanks. Most auto parts stores carry it. The first patch lasted a couple of years and I just put a new one on. Too tiny to justify removing the tank and too big to ignore (constant raw gas smell).

If you find a small leak and decide to try it, take your gas cap off first to make sure there's no pressure pushing gas out of the hole while you're sticking the patch on.