Getting 97psi fuel pressure ... help

[Kegworth]

Been doin all the things to get truck runnin smooth. Vacuum lines replaced, gaskets replaced, cleaned IAC, and finally got a fuel pressure tester and it’s reading about 70psi in key on engine off, and about 97+ Engine on!!!

i was certain it was the FPR so i just replaced that and it did nothing.
Also, noteworthy, it does not hold pressure. After engine off, pressure remains but drops to about 10-15psi after approx 2-4 minutes.
Thoughts ?

 

[Uncle Gump]

Do you have a good manifold vacuum hose to the regulator? They require a vacuum reference...

 

[RonD]

Remove the fuel line on the FPR and blow thru it, that is the RETURN line back to the gas tank so is OPEN at the other end, but if tank is full you need to blow hard to get it to bubble up inside the tank
If that hose is clogged then FPR can't release fuel back to the tank, can't control pressure

OR

you may have a bad pressure gauge, the fuel pump is certainly capable of 70+psi, 90+ would be a stretch

And...............if pressure is dropping to say 15psi key off, then with key on, ONE TIME, engine off, you should only see a 10psi increase in pressure, if its more then gauge is bad
Pump only runs for 2 seconds key on, then doesn't run again until engine starts, above 400rpms
Each 2 second run time is about 10psi increase

Test gauge on a tire, air pressure, same schrader valve is use for both

 

[Kegworth]

Remove the fuel line on the FPR and blow thru it, that is the RETURN line back to the gas tank so is OPEN at the other end, but if tank is full you need to blow hard to get it to bubble up inside the tank
If that hose is clogged then FPR can't release fuel back to the tank, can't control pressure

OR

you may have a bad pressure gauge, the fuel pump is certainly capable of 70+psi, 90+ would be a stretch

And...............if pressure is dropping to say 15psi key off, then with key on, ONE TIME, engine off, you should only see a 10psi increase in pressure, if its more then gauge is bad
Pump only runs for 2 seconds key on, then doesn't run again until engine starts, above 400rpms
Each 2 second run time is about 10psi increase

Test gauge on a tire, air pressure, same schrader valve is use for both

Great idea to test on tire. Will do that now....

And yes, to the previous post, the vac line is good to the FPR.

 

[Kegworth]

Just checked tire pressure and it came out identical on both gauges. Soooooo. That 97 PSI is no joke. Could that much pressure really be caused by a clogged return line?

 

[RonD]

Sure, I would think around 70psi would be the upper limit, but never tested how high a fuel pump can go
Computer would have set RICH codes if FPR wasn't working or return was blocked and pressure was high, usually over 50psi would set rich codes

And on cold start you should be seeing grey smoke out the tail pipe until engine warmed up and computer could adjust for the higher pressure

FPR should open at about 43psi engine off, 35psi engine at idle(thats what vacuum line is for)
You can have the Fuel Return line off the FPR and put a towel down then cycle key on and off, a few times, no fuel should come out of the FPR port until pressure gets above 40psi

 

[Kegworth]

Just tried to get the new FPR return line off the barb anddddd can't. Its too tight. Lol. Guess i'll just cut it off and have to replace it with a new one in order to do the blow test... smh. The engine seems to hate life. Cold start running at around 800rpm, didn't run above 1k, not even for a moment. Feels rough and heavy, if that makes sense.

Not seeing any grey smoke though. Whats odd is just two days ago it seemed to running significantly better, i let it idle for about 25 minutes. That was before i even knew about the fuel pressure issue. Haven't driven it anywhere either. #lost

 

[RonD]

Image here of a 1988 Ranger fuel pump assembly: https://ic.carid.com/airtex/fuel-pump/e2095s_1.jpg

Return line has the little red screen filter on the end, down next to the pump

Since its a 1988 does it have 2 fuel pumps?
And the canister type filter near the gas tank?
And does that canister have 2 OR 4 hoses attached?

 

[Kegworth]

I had two tanks, yes... but have since deleted the rear tank and plugged the hoses from the old rear tank.
But yes there are also two filters, and in line one and one mounted on frame rail.
I’m fairly sure it has 4 hoses but will double check it tomo.
What are you getting at? @RonD

 

[RonD]

Well..............the return line may run thru one of the canisters

And if you had dual tanks then return lines also needed to be switched, along with pump lines, when tank was switched

So there would be connectors for that
2 fuel lines from each tank to the switch, so 4 lines, and then 2 lines out to the engine, 6 port switch/valve
The switch changed pump and return lines both at the same time

Full size used something like this: http://www.supermotors.net/getfile/669589/fullsize/d01assembled.jpg

Not sure what Rangers used for dual tanks

But some used these types for single tank: https://cimg6.ibsrv.net/gimg/www.ra..._8350b2f018774c26bb244229ac6cf4c4ef1cb739.jpg
Return goes thru it

 

[Kegworth]

Okay, I’ll process all that and confirm what i have. But just trying to figure out what you’re implying? That the fuel switch valve is bad? Or blocked or something?

 

[Snoranger]

Okay, I’ll process all that and confirm what i have. But just trying to figure out what you’re implying? That the fuel switch valve is bad? Or blocked or something?

It sounds like the return line is plugged solid. 97 PSI is WAY more than that system is designed... it’s probably got the pump screaming for its dear life.

 

[RonD]

Yes, on most Rangers, 1989 and up, the return line just ran straight back to the gas tank, just 1 connection on each end, nothing in between

In yours there may be more connections on the return line, so maybe another part that could be clogged up
A clogged return line is very, very, unusual

 

[Kegworth]

If that’s the case, and the return line runs to the tank selector valve, maybe i can run a new line or take the main line and run it directly to the tank now since I’ve removed the secondary tank. Assuming that line is clear.
Gonna give that a go tomo morning.

 

[RonD]

Well if you disconnect the return line(from engine) at the selector switch and put a container under it, you could see if fuel came out and pressure dropped to 30psi with engine running

A return line has No Pressure, so if it is the selector that's blocking it you can just use 5/16 barb connector/union and clamps to by pass selector