Fuel 90 5.0 LX

dwb · Jul 11, 2018

Afternoon all.

I have read some others issues with fuel pressure and tried some suggestions and nothing seems to work. As most car issues can be specific to the whip.. here goes.

I put in a Walbro 255lph fuel pump few weeks ago and new fuel filter..

I bought an adjustable Aeromotive FPR (35-70 psi)

Hooked up a fuel pressure guage to make sure all was right and got 0 psi. But the car runs fine.

When I turn the key on the pump primes and i noticed the fuel pressure goes up to 10 then drops. I can keep Turning the key on and off a few times and the pressure will only go to 30 but drops right after the 2 second prime time.

Car running at idle the pressure is 30. I adjusted the FPR to see if I could get it up but maxes out at 35.
Thought the pressure would be 39 running ? So wrong FPR? Do I need a 30-65 one ?

Thoughts, suggestions would be appreciated

No codes other than 15 and 51 (koeo)

Also, the process to test fuel... take off the vaccume line and plug it? Leave the fitting on the FPR where that line goes open or plug that too?

jrichker · Jul 11, 2018

Check fuel pressure:
The local auto parts store may rent or loan a fuel pressure test gauge if you don't have one.
Disconnect the vacuum line from the fuel pressure regulator. Check it for evidence of fuel present in the line by removing it and blowing air through it. If you find fuel, the fuel pressure regulator has failed. Reinstall the line; leave the fuel pressure regulator end of the vacuum line disconnected. Then cap or plug the open end of the vacuum line and stow it out of the way.
Connect the fuel pressure test gauge to the Schrader port located just behind the alternator.
Turn the ignition switch on & start the engine. Observe the pressure: you should see 38-41 PSI at idle.
Turn the ignition off; reconnect the vacuum line to the fuel pressure regulator. Then disconnect the fuel pressure test gauge. Watch out for squirting gas when you do this.

Fuel pump pressure test
Disconnect the larger of the two fuel lines up by the Schrader valve. It is the return line and does not have the Schrader valve on it. Find a piece of rubber fuel hose and clamp it on the return line coming from the regulator. Stick a bolt in the other end of the hose and make sure that all your connections are tight and leak proof as possible. When this powers up, you don't want fuel squirting everywhere. Hook up the fuel pressure test gauge. Turn the ignition switch on and watch for leaks. You may want to use a helper inside the car to cut the switch off quickly if you have a leak. To trick the fuel pump into running, find the ECC test connector and jump the connector in the Upper RH corner to ground.

Caution!!! You have blocked the return line for the fuel pump! Pressure will rise very quickly past safe levels with a good pump
If the pressure goes up past 55 PSI, the pump is good and the fuel pressure regulator is bad. If the fuel pressure does not hit 55 PSI or more in a few seconds, the pump is bad or you have electrical problems.

dwb · Jul 11, 2018

Alright I will try a few more things. I can’t get the pressure higher than 35 which vehicle at idle even when adjusting the FPR all the way clockwise.

Boostedpimp · Jul 12, 2018

Toss the factory regulator back on and see if you get the fuel pressure your missing back. Unless your car has a good bit of modifications you don't really need an adjustable fuel pressure regulator.

dwb · Jul 1, 2019

Well. Here we are again.
Put the stock FPR back on. Same thing. No pressure at the Schrader valve. I can depress the value and fuel comes out. But turning the key on or even the engine on, gauge reads zero.
It’s a new fuel pressure gauge (returned one just Incase but same thing )

Car starts up good. Idles good (finally) just wanting to check fuel pressure.

Also have a vacumm leak. Only reads about 8

Boostedpimp · Jul 2, 2019

Does the car have aftermarket fuel rails? where is the fuel pressure gauge screwed in? Post a pic of your engine?

dwb · Jul 2, 2019

Still stock fuel rails. Sorry it’s a fuel pressure test gauge not an actual fixed gauge. I have it hooked into the schrader valve.

I will get an update picture later today

a91what · Jul 2, 2019

did you secure the fuel line to the pump when you installed it?

dwb · Jul 2, 2019

That was my next play. Go into the tank to have a look. I was a little worried that little filter on the pump would fall off. Didn’t seem to be secured that great then getting it seated in the tank hopefully it didn’t fall off. Not sure what would go on not having that filter.

But I will check all the lines.

I would imagine 39ish PSI fuel pressure when you depress the schrader valve pin the fuel would spray out with some pressure to it. When I depress it fuel comes out but not under pressure. I’ll also get a video

dwb · Jul 2, 2019

Here are some pictures of the engine

- Is it okay to check vacuum pressure from the originally capped off port on the vacuum tree? (B/R)
- - getting a consistent 8 on the test gauge

- Fuel gauge is plugged into the Schrader Valve
- - fuel comes out when you depress the pin or while screwing on the test gauge fitting

- that melted vacumm block - thingy magiggy
- - I deleted smog and EGR (drive maybe 300 miles a year)
- - - I have the SVE EGR delete kit from LMR
- - - -two are capped 2 are melted closed (Hoses touched the header)

jrichker · Jul 3, 2019

dwb said:
Alright I will try a few more things. I can’t get the pressure higher than 35 which vehicle at idle even when adjusting the FPR all the way clockwise.

Did you do the fuel pressure test that I posted? What were the results when you blocked the fuel return line?

dwb · Jul 4, 2019

Something has to be wrong with my Schrader valve or I can’t screw a regulator hose on a bicycle fitting to save my life.

This is the second test gauge and I get nothing on the needle. Not even a flinch.

The car starts up no problem.. runs.. wouldn’t I at least get something on the dial ?

General karthief · Jul 5, 2019

Let the car sit over night so you know there is no pressure, take a valve stem removal tool and take the schrader valve out and inspect it.

dwb · Jul 6, 2019

Okay
Replaced the valve stem.. got a new ford schrader valve adaptor and now I get readings. (Might have been my schrader adaptor because the old one didn’t work with the new stem)

When I turn the key on.. the pressure goes up to 10.. so I adjusted the fuel pressure regulator and I get like 45ish then drops to 25/26. Trying to do my adjustments but if I get it down to 38-39 when first turn key on it will hit that 38-39 but then drop to 25.

Should it be a constant 38-39 with just Key on?

dwb · Jul 6, 2019

Key on. Pump on - 45 ish
Pump stops priming drops to like 25/26

This was the first adjustment. So lowered it where it will hit 38-39 key on then drop to 25/26 when pump stops priming

dwb · Jul 7, 2019

I have an aeromotive AFPR and read they bleed down a bit.

“One guy supposedly contacted Aeromotive and was told that they bleed down to prevent fuel heat soak in the rail or something along those lines.”

Should I just lower that initial prime down to the 38/39 range ? And then check pressure with engine on? (Too late to fire up now)

General karthief · Jul 7, 2019

When you first turn the key on the pump 'primes' the fuel system, the pump will not continue to run unless the engine starts or you 'fool' it buy jumping it. Check koeo pressure around 40lbs +\- then it will fall off, koer pressure should be around 35lbs+/-
the proper fuel pressure test is with the koer and vacuum line off 40-42 lbs vacuum line on 34-36 lbs

Mustang5L5 · Jul 7, 2019

Should be doing this with engine running.

Engine off and you are taking the efficiency of the fuel pump check valve into account.

Engine running, vac line off and plugged...set to 39psi.

When you shut the engine off it will do any number of things. On my old pump with a blown check valve it drops instantly to zero

dwb · Jul 7, 2019

Thanks for your advice all. Did the adjustments and the car runs better now than it has the last 2 years.
Few tinkering to deal with the MAF as it still has a bit of hesitation but I know moving that MAF sensor a bit helps.
And some backfiring when letting off the gas so. Will tackle that.
Thanks again

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