Hello, I recently had some fuel related problems with my jeep and I replaced the fuel pump and it was running great. For a couple of days. The previous owner had already relocated the in-tank fuel pump and replaced it with an inline Edelbrock which was only capable of 4-7psi. I ended up putting a much stronger in-line pump taking the advice from some other random forum. I installed a NAPA P/N: B0129E. After installing it, it was instantly better. 14psi at the test port, more throttle response, no hesitation, no backfire, no miss, just running real good, so good that I took it out on several deliveries at work today. After I got back from one though I parked, unloaded some returns, and went to move it into a different spot and the fuel pressure had clearly dropped (didn't want to idle, giving it gas would kill the engine, and

I have not done much diagnosing yet other than looking at my fuel pressure at the test port on the throttle body and noticed the pressure was about 6psi. I suspect that this stronger pump may have caused the fuel pressure regulator diaphragm to fail so I am I definitely know I have another fuel issue, but ultimately what I am asking is: How do I check the fuel pressure regulator on a TBI 2.5l ?

 

From my '88 FSM in the 2.5L TBI section:

FUEL PRESSURE REGULATOR
WARNING: Always relieve residual fuel pressure in fuel delivery system before opening system. To prevent chance of personal injury, cover fittings with shop towel while disconnecting fittings.

1) Replacement fuel pressure regulator must be adjusted to establish correct pressure. Remove air filter elbow and hose. Connect tachometer leads to diagnostic connector D1, attaching negative lead to terminal D1-3 and positive lead to terminal D1-1.

Remove screw plug and install fuel pressure test fitting.
NOTE: Fuel pressure test fitting is not included with throttle body. Fitting (8983 501 572) must be obtained separately.

2) Connect fuel pressure gauge to test fitting. Start engine and increase speed to approximately 2000 RPM. Turn Torx head screw at bottom of regulator to set correct pressure. Turning screw inward increases pressure and turning screw outward decreases pressure.

3) All models require fuel pressure of 14.5 psi (1.0 kg/cm ). Install lead sealing ball to cover regulator adjustment screw after adjusting fuel pressure. Turn ignition off. Remove measuring equipment and test fitting. Install original plug screw and air filter assembly.

You can find the FSM at Cruiser54's site:

https://cruiser54.com/?page_id=365

Looks like you can remove the cover from the regulator and inspect the diaphragm. Also looks like the part is available from Rockauto.

https://www.rockauto.com/en/catalog/...regulator,6124

 

Thanks for the response. I have a throttle body rebuild kit, injector, and the in-tank fuel pump on order - just in case.

I was under the impression I would be getting too much fuel pressure if the regulator failed, not too little of it. So I feel a little stumped. It doesn't act like the engine is getting flooded of fuel but starved of it. The fuel filter was changed right before the new fuel pump so I don't think that it would be contributing, but I may replace it for safe measure and see what happens.

If there is no improvement then I will take the throttle body unit apart and inspect the fuel pressure regulator. If the diaphragm is torn it will be apparent that I put too big of a fuel pump on it and I have to downsize.

The more I ponder on it though the more I believe the fuel filter is causing my issue.

 

It certainly could. Is the external pump installed before or after the filter?

The fuel pump module is accessible without dropping the tank. Makes me wonder why the PO didn't replace the pump with the proper one.

 

I found this bit in the FSM last night about testing the regulator:

I pinched my return line and did not see any fluctuation in pressure at all, so I proceeded to the filter which did prove to solve the issue.

I have a suspicion that the original pump is in the tank still but went out, or had a hose rot off so stopped moving fuel. I should have dropped the tank and done more diagnosing but it is half full so I opt against it for today.

 

So, I ended up having another filter clog on me yesterday after a decent little drive.

The external pump is installed before the filter. I am considering installing another smaller filter right after then pump itself, I wanted to install it before but someone suggest it is better after because it could clog and run the pump dry.
I may need to replace the tank or drop it and flush it. The PO may have been just as blind as me and not seen it was accessible from the side of the tank. I didn't even read that you said it until I re read it in an email, and I didn't even really comprehend it until I looked up buying a replacement tank and saw a picture of the tank.

Does anyone have any advice on getting rust flakes out of a gas tank?