pr1689

Well my son drove his car to his college apartment and once parked, it wouldn't start again. I was headed there anyway to bring his things for his apartment. I didn't have any tools with me so I bought a really cheap set of tools from a local autopart store and tried to diagnose the problem.

The distributor bug was turning fine and he has spark. This was tested by attaching a spare spark plug to a plug wire and holding it against the engine block and turning the engine over.

When he turns the key to on I can hear the fuel pump relay activate for about 2 seconds.

When I press on the schrader valve gas does come out but it doesn't spray out, so I think its not having enough pressure to the fuel injectors and therefore no gas is getting through.

I replaced the fuel pump a year ago July, and I'd hate to drop the tank again and replace the fuel pump, but will do so if I need to.

I know I can check the fuel pressure with a gauge, which I have, but my question is, how can I tell if its the fuel pressure regulator or even possible the fuel pump relay?

If the fpr is faulty, won't that also cause the fuel pressure to be low? Its the original one and hasn't ever been changed. Would it be a good idea to go ahead and replace it with an adjustable fpr? If so, what is a good one to purchase.

If it turns out to be the fuel pump, what brand do you all recommend? I bought one last year from Advanced and this time figured I'd not go the cheap route as I don't like having to drop the gas tank again.

Oh, the car is an 86 IROC Z28, tpi, 350 engine, automatic.

Thanks for any and all advice. I've tried searching and am having trouble finding answers to my questions.

Thanks,

Pat

raptor80dad

Try unhooking the MAF.I had an 89 IROC TPI same problem

good luck

pr1689

Hmmm, so the Mass Air Flow sensor on the snorkel could cause this? I guess it could since it deals with the air flow.

One other thing I left out of my long post was that he stated it did it when he first got to the apartment after driving about 2 hours, and he went in, signed his lease and got his key. He said when he started the car it was idling really poorly and when he gave it some gas it smoothed out. Then after parking it the 2nd time, that's when it wouldn't ever start up again.

I'll call and have him unplug the maf and see if it starts.

Thanks for the suggestion!

Pat

raptor80dad

I think it screws with the ECU.

pr1689

Ok, great. I've called my son to have him try this as soon as he gets back to his apartment. I'll post back how it turns out.

I just don't want to drive 2 hours there and 2 hours back only to find out that it's not the fuel pump and some relay or sensor. :-)

If its not the MAF, I have a feeling its either the fuel pump, the fpr, or possibly the fuel pump relay. It does energize and I can hear it, but when I press on the schrader valve on the fuel rail, it doesn't seem like its under a lot of pressure. I'll have to put some money in his account so he can go buy a pressure gauge and check the pressure once the key is turned on and the car is cranking. IIRC, that should be around 40 psi or so.

If the fpr is faulty, won't that also affect the pressure? How would I be able to tell if its faulty over the fuel pump?

Thanks,

Pat

pr1689

Well, it appears to not be the MAF. He said he unplugged it and still it didn't want to start. He said that he can hear the fuel pump energize when he lefts off the key when trying to start, but didn't think he heard it when he initially turned the key to on.

Sound like a fuel pump relay maybe?

Its really difficult without having the car here to try and diagnose things.

Thanks,

Pat

pr1689

Something else I should mention. The connector to the oil pressure sending unit (OPSU) won't stay on and keeps popping off, so we've left it off for the last year. The car has run fine without it, so we never worried about it.

I do know that when I jumper between the two wires, I can hear the pump working, but what I'm not sure about is the pressure. We tried starting the car with that jumpered, and it still wouldn't start. So I have to wonder if its just not getting enough pressure.

Any ideas anyone?

Thanks,

Pat

raptor80dad

That sending unit must just be for the gauge.
You could spray a little starting fluid in the plenum and see what happens,if it starts then you could have a fuel issue.
If you hear the pump running and it sounds strong and shuts off after a few seconds then it is probably making the proper p.s.i. and the relay is working.
I would definitely check the pressure on the rail.If it isn't steady 40-43psi I would invest in a service manual like Hayne's,that will help you in tracing the problem and are very handy to have .
Good luck,Mike

you could try the relay anyway,only$15-20

pr1689

Thanks Mike for the reply. I've got several manuals for the car, but wanted to get people's thoughts who might have experienced this as well. I'll know more once he gets the fuel pressure gauge on there.

I was really trying to figure out how to distinguish if the fpr was faulty or if it specifically is the fuel pump. If the fuel pressure is low, it could be either, so I wasn't sure if there was a test for the fpr or not.

Anyone know how to do this?

Thanks,

Pat

ap72

If its the relay the pump won't click on at all, so its 99.99% chance that its not the relay. You can "dead head" the return line to test if it runs with the full pressure of the pump, if it does then it is the FPR- but that's also not likely.

What is likely is a clogged fuel filter. Its very likely and a very cheap fix. i would swap the filter and try it. Its only a few bucks AND it never hurts to replace a filter. I've seen clogged filters cause this problem on a LOT of cars.

pr1689

Ok, sounds like a plan. I'm kinda questionable that its the fuel filter since we put one on about 3 months ago.

I have to wonder if its not holding pressure. When I had jumpered the connector on the OPSU, I could hear the pump running but under the hood it sounded like I could hear flow, a swooshing sound in the plenum.

So I have to wonder now if the fpr is faulty or if I have leaky injectors. What's the best way to tell if I have an injector leaking? Would a single injector prevent the car from starting if it was leaking?

Thanks,

Pat