born2sleep13

Hey fella need some help with this as I am stuck.

Car idles but will bog with throttle. Got a B&M fuel pressure gauge and it is only reading 5-10 psi. With the pressure regulator disconnected at the rail, the fuel prime pumps a considerable amount of fuel out. It just doesn't seem to hold pressure in the system.

I have completely drained the tank and added new premium, checked all the lines, no cracks or leaks visible. Disconnected line at both ends and blew them out with an air compressor, so no clogs. I have replaced the pump with a new walbro 190 with new sock(pump filter). New fuel filter. New AEM fuel pressure regulator.

Nothing has changed the fuel pressure. When the pres reg is disconnected at the rail, the prime pumps a good amount of fuel out, it just appears the system will not hold the pressure.

My only other thought is maybe an injector stuck open. I'm not sure how to check for this. The FSM doesn't go into much detail on troubleshooting low fuel pressure. It only says check for leaks, clogs, or fault pressure regulator.

Anything else I should check or thoughts on this issue.

NotARaCist

iTrader: (1)

Actually, the FSM does go into great detail about loss of fuel pressure. It sounds like your FPR has failed, though. Replace it with an OEM unit.

delsolintegra

This may sound off the wall but i have a 93 del sol si with the D16Z6 that had a bogging problem and also would only start when the engine was cold, not when the engine is warm. I checked and replaced a lot of things over time both ignition and fuel related but what the problem was, was a bad coolant temp sensor. This confused the ECU and fuel flow was off and it seemed like a fuel pressure anomaly to me. $20 coolant temp sensor made a world of difference.

NotARaCist

iTrader: (1)

Completely irrelevant to OP's problem.

delsolintegra

OP Your hunch about a fuel injector being stuck open.

When the coolant temp sensor fails the ECU thinks it is providing fuel requirements to a cold engine all the time. The ECU will increase injector timing to allow more fuel to flow, for cold starts and to run a cold engine. This increased fuel flow will make fuel pressure appear to drop. If you check your spark plug color and it appears to be more light grey as opposed to be tannish white you are running too rich. This is a hint that your ECU thinks it's running a cold engine all the time.

I never got a Cel light for a failed coolant temp sensor. It's a subtle problem and I went thru swapping FPR's etc..

If my 1993 coolant temp sensor can fail now at 22 years old, so can yours.

born2sleep13

narc: the FPR has been replaced with new aem, no change still reading low pressure.

tegra: if you are talking about the one on the dizzy side of the block with the 2 prongs I have changed that one for new. the sending unit (single post) was not replaced dont know how that works with it, guessing single post for the temp gauge and the 2 prong sends to the ECU.

Plugs are black down on the threads, prong and the tip look clean

Wish I could see what the computer sees.

NotARaCist

iTrader: (1)

I didn't say new AEM, now did I? I said OEM for a reason. First off, nothing in your thread indicates that you actually need an adjustable FPR. Second off, the AEM FPRs have been notorious, especially recently, for having failed or failing diaphragms, even fresh out of the box. Third, safe bet you haven't adjusted that thing, and it's quite possible that you don't actually know how to do so.

Do I need to keep going?

Leaking injectors are extremely easy to diagnose. Turn the key to ON(II). Let the system pressurize. Turn the key OFF. The system should hold pressure for 3 hours, losing no more than 1 PSI. This procedure is also in the FSM.

born2sleep13

Okay did not know that about the aem FPR. I got it because I will be doing a turbo build soon and thought it would be beneficial in the long run. I have tried other oem FRPs and nothing has held the pressure. The prime will only run up to 5-10 on prime and drop to 0 withing seconds on the pump kicking off.

Guess I will have to dig in the FSM a little more. I did not see that procedure for testing injectors.

I do know how to adjust it and have tried shifting it for affect but it does not change the pressure at the filter

NotARaCist

iTrader: (1)

It isn't necessary unless you're pushing stupidly high numbers. If pressure is immediately being released, either you have a leak (could be in the line, could be in the rail, could be in the injectors), or your FPR is bad.

Start off by doing these tests. Go ahead and use the AEM FPR. When it fails, get an OEM FPR and repeat the tests. We can work from there.

born2sleep13

Ok I guess I will just keep looking for a leak. I will try throwing on the oem frps too just to see. Thought I might be missing something stupid.

Thanks narc

NotARaCist

iTrader: (1)

Yep, no problem. Keep in mind that, until you have a properly functioning FPR, my previous test for a fuel injector leak is functionally useless.

born2sleep13

yeah if I can get the system to hold the right pressure I then I can check the injectors. I need to get it on a lift to really inspect the fuel lines. It just baffles me because usually you would see some fluid somewhere to help indicate.

UV dye test? just kidding, hope you jumped a little

NotARaCist

iTrader: (1)

I mean, you joke, but it works. Only takes a little bit of UV dye, a dark room (or night time), and a black light

born2sleep13

Well fellas this thread has been solved. After weeks of troubleshooting and lots of anger, violence, and vulgarity, I found the culprit of the low fuel pressure. It was the soft line from the pump to the access panel to the top of the tank. It had a pretty large hole in it, just pumping fuel back into the tank. New line, fired right up. She still needs some loving in other places but she is alive again. Thanks for the support dudes.