87 fuel pressure regulator

[purplepeopleeater]

Hey everyone, I have a quick hopefully simple question. Would a bad fuel pressure regulator cause a 2.9 to die right after start up? There is fuel in the small vacuum hose, so I know it's bad, and when I unplug the vacuum line on the other side of the intake(pass side). The truck will run and idle, not smoothly, but it will stay running. I Should have the regulator in today, but I'm hoping for other areas to look if it doesn't fix the problem. Thank you for any help your willing to provide.


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[RonD]

Yes, bad regulator could cause that symptom.

Fuel pump only gets power for 2 seconds when key is turned on.
It won't come on again until engine RPMs are above 400, engine started

That 2 seconds is about 10psi of pressure, assuming bad regulator leaves it at 0 psi when engine is off.
So when engine starts that 10psi is used up pretty fast and it drops close to 0 again before fuel pump can come on and build it back up to normal 30-40psi.
So engine may stall and certainly stumble on startup.

And the fuel in the vacuum line can build up cause engine to flood temporarily on warm start, or even cold start

 

[purplepeopleeater]

Yes, bad regulator could cause that symptom.

Fuel pump only gets power for 2 seconds when key is turned on.
It won't come on again until engine RPMs are above 400, engine started

That 2 seconds is about 10psi of pressure, assuming bad regulator leaves it at 0 psi when engine is off.
So when engine starts that 10psi is used up pretty fast and it drops close to 0 again before fuel pump can come on and build it back up to normal 30-40psi.
So engine may stall and certainly stumble on startup.

And the fuel in the vacuum line can build up cause engine to flood temporarily on warm start, or even cold start

Excellent, just what I'm was hoping to hear. Thank you very much for the help


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[Pauls 4x4]

Mine does this and I replaced the FPR with motorcraft bits. I figure it's either a bad check ball in the pump (but I ain't gonna chase that $$) or it's related to whatever is giving me a 2% rough idle and surge at warm started > 30 mph that I just can't figure out (probably ECT or ECM loom).

 

[purplepeopleeater]

I would like to confirm that replacing the regulator helped my problem, but since doing so, the truck doesn't want to ignite the fuel it's getting, the coil has slightly higher resistance then the supposed ok range. I think it's either the coil or the ignition control module on the distributor, may also effect idle quality id imagine


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[RonD]

A coil is just what it says, "a coil of wire", wrapped around a metal core, so should have low OHMS(resistance) since it is just a coil of wire.
Generally an automotive coil will show under 1ohm, .3 to .9, on the Primary side, 0 ohms is a short.

Spark plug gap needs to be 0.044 so fairly wide, wider gaps gives hotter spark, but less recovery time for coil at RPMs above 3,000.
Car makers spec the average gap for average driving, you have a +/- range of .005
So better cold starts and low RPM driving would be .047-.049
If you were racing the engine then .041-.039

'87 2.9l need to be manually timed for spark.