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2.9l Fuel pressure question


CrowRanger

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So, randomly while working on a customers car. i needed to check their fuel pressure, wasnt getting a reading on my gauge despite some visible (but small) pressure so i wanted to double check my gauge and get a control. so i hooked it up to my truck and it was 20 PSI KOEO and KOER. which is waaay below spec.
ive had teh truck for years, practically rebuilt the whole thing but the bottom end. its in good running shape, it doesnt idle bad, doesnt run bad, its not a power house either, lifted, big tires, small gear ratio, i dont expect it to chirp the tires, but i mean its always felt sluggish, but acceptably.
The only odd things that have ever happened, is during the colder months, when i crank it, it will start then stall immediately and the start back up right away on the second crank, everytime without doubt for years. just how she is.
and occasionally, she'll stumble a bit and rpm drop down for no reason every other month.
i can rev it all the way to the limiter in every gear (if i had enough time and space in 4th and 5th hahaha) never bogs down.
i guess the only other things that comes to mind is, but i cant find any info on the spec for it. the engine runs at 13-15 inHg vacuum. which always has, no vacuum leaks, 160 PSI compression in every cylinder. so i never thought twice about it.

Anyways... my point :popcorn:
Im all paranoid now that i saw 20 PSI, and wondering if my truck has been starving for gas for ages, no lean codes. im tempted to just go buy a new fuel pump anyways to see if my engine will come to life (lol doubtful)
or should i just leave it alone, if it aint broke dont fix it?:icon_confused:

and any info on the vacuum pressure spec would (or what yours is) be nice too.

cheers mate
 


CrowRanger

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Guess i should of put this in the 2.9l section. mods move please n thank you. i shouldnt forum on lack of sleep
 

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bf750

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2.9 fuel pressure should be at 35 to 43 psi
 

CrowRanger

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2.9 fuel pressure should be at 35 to 43 psi
Yes i know that, hence the entire post and me saying its not in spec, the question was, if its ran fine forever like that, is it worth changing it/would i notice a difference.
 

adsm08

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i shouldnt forum on lack of sleep
Oh how true this is. Forums should be treated like heavy equipment and not operated under the influence of drugs, alcohol, bad attitude or little sleep.

Anyway, that pressure sounds low. I don't like to use static pressures for diagnostics on return-type fuel systems though. I have found that the static pressure bleeds down very quickly, even though there is no real problem.
 

CrowRanger

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Yeah i havnt done any testing into it, just running and pump on as well as all off and it held at 20 psi the whole time. Was in the middle of a job so just said forget it and went back to work.
Far as i know its the stock pump. everything ive replaced on the truck has been stock. so 25 years is pretty good.

Once the sun drops down ill go test it, to hot to be outside.

ill see if it changes with regulator unplugged and such. you think opperating at that pressure the return wouldnt even open so really pulling the vacuum off the regulator shouldnt do anything, wonder if the return line is dry.
I had to go and check it.. may as well just light my money on fire haha. least i dont have to pay for labor i guess..
 

CrowRanger

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So, checked it out again just now.

KOEO, same with ER 17-18psi. would shoot up to about 25 with reg unplugged.
all in all, its acting normal, the regulator is working. which is weird in my mind. because there shouldnt be a fluctuation in pressure unplugging the regulator if the pressure is below regulated pressure to begin with. Correct me if im wrong on that.
maybe theres something wrong with my gauge?


adsm08, you seem like someone who would know the answer to my other question, on what the Vacuum reading 'should' be for a 2.9l? though doesnt have anything to really do with this other issue.
 

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