87 F150 Won’t Start

[RonD]

Just plug off the smaller one, it may be for another device that needs/uses vacuum

 

[Mhfco6]

Just plug off the smaller one, it may be for another device that needs/uses vacuum

The PCV valve And new grommet is installed, PCV valve came with a cap to “break off” almost like a model car part. It was used to plug off the extra line.

After much frustration I was able to disconnect the return line behind the intake plenum and blow air through the line, all the way back to the tank. I ran the truck and watched the gauge creep up to 85 and I shut it off.

Regulator is bad?? Can this be done without removal of intake manifold?

 

[Mhfco6]

The answer is, NO, haha! Hope the regulator is the issue after all this. Can you test these regulators? If I blow air into the supply side of regulator, air pressure comes out of the returns side. On the fuel rail, if I blow air in the return side of regulator plate it goes all the way to the tank. If I blow air into the supply side, the rail gets pressurized, via the gauge.

Even though the regulator is removed I still have pressure on the rail gauge. It is slowly loosing psi over time, like usual.

 

[Mhfco6]

The new fuel pump regulator didn’t do anything, pressures are still through the roof.

What will a high alititude ECU do on a normal truck??

 

[rusty ol ranger]

High alititude ECMs will be leaner across the board because of thinner air at high altitudes.

How high is the pressure? IIRC the 300 calls for like 65lbs

 

[Mhfco6]

High alititude ECMs will be leaner across the board because of thinner air at high altitudes.

How high is the pressure? IIRC the 300 calls for like 65lbs

It will wrap the gauge if I let it run that long 100+. I just called to confirm this ECU is not a High Altitude, but IS a 49 state ECU. Cardone part# 78-4464 (E7TF-KA)

 

[rusty ol ranger]

It will wrap the gauge if I let it run that long 100+

Um id get a new gauge. At those pressures you would be exploding lines. I dont even think the pump is capable of that.

BTW...i found this PDF that lists fuel pressures from some tech colleges book. I couldnt link but heres a screenshot...

I was close lol.

 

[Mhfco6]

Um id get a new gauge. At those pressures you would be exploding lines. I dont even think the pump is capable of that.

BTW...i found this PDF that lists fuel pressures from some tech colleges book. I couldnt link but heres a screenshot...

View attachment 50898

I was close lol.

I like your “close enough” better than my 100psi, haha. I’ve tried a couple different gauges.. maybe I need to get a true liquid filled and try that.

 

[rusty ol ranger]

I like your “close enough” better than my 100psi, haha. I’ve tried a couple different gauges.. maybe I need to get a true liquid filled and try that.

@adsm08 @RonD is the pump even capable of that kind of pressure?

 

[RonD]

@adsm08 @RonD is the pump even capable of that kind of pressure?

Apparently it is, lol

A while back I was testing an FPR and clamped off the return line, I think I got just above 70psi

You could screw gauge on to a tire, same fitting, and see, assuming you know the tire's pressure

 

[Mhfco6]

Apparently it is, lol

A while back I was testing an FPR and clamped off the return line, I think I got just above 70psi

You could screw gauge on to a tire, same fitting, and see, assuming you know the tire's pressure

I did this already with current and a different gauge. I did not try the whole line set, but I will.

 

[Mhfco6]

Alright I unplugged the return line at the pump to physically watch fuel flow from the line. At the the same time the truck ran, and I watched the fuel pressure gauge. I then hooked the line back up to the pump and rewatched the gauge. The truck ran a total of 15 minutes and pressures did not go above 42psi. Not sure what I did, but this issue may have resolved it self. 3rd times the charm?

 

[RonD]

Good stuff

Yes, that was an odd one

 

[Mhfco6]

Good stuff

Yes, that was an odd one

I ran a second test, and let truck run for an entire hour. Run time and PSI are as follows:
25 mins: 70 psi
35 mins: 75 psi
47 mins: 78 psi
1 hour: 71 psi

Nice to see it went back down at some point. It seems to be getting better and hopefully will only get better with time.

 

[Mhfco6]

While driving the truck the other day I noticed having to hit the breaks harder than normal to stop. Then as I slowed and sat the idle was really high. I’ve checked vacuum lines checked timing again.. but no luck. I backed out the throttle screw all the way, but idle is still screaming. Any ideas?