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Fuel pressure issue, missing when wot.


Bracket racer

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Out wheeling the other night and shut off for 20 minutes or so. Went to start and it rolled over like it was flooded, caught on a couple cyl's and puttered for a minute then finally revved up but was skipping bad. Idled fine, light throttle it would rev to 4500. Stomp it and it was like shutting off the key. Half to the floor and it would skip and fart as it slowly revved up.
So, idled away (was crawling anyway) and after 5 minutes of driving it still skipped but revved better. After 15-20 minutes of crawling (1st gear idle over rocks) stabbed it and it took off, no missing. Tried again and from idle to 5000 was clean, no skipping.

Today I checked the fuel pressure and koeo it was 20-25psi. Threw on a new fuel filter it went to 30psi. Engine running or not it maxes out at 30psi.
Pulled the vacuum line off the regulator and the needle went crazy, vibrating between 25-35. Plugged it back in, steady 30.
Turned key off, holds 30psi for a while but when I check 5-10 minutes later it's a 25 or so.
Turn the key on and leave it on, the fuel pump cycles about every 3-4 seconds. Runs, pressure goes up, then off for 3-4 and then it kicks in again, continually until I shut the key off.
I heard a clicking while the key was on, separate from the relay, it was the injectors. (Why are they clicking?) Also, if I start it up, shut it off, start it up, shut it off it fires up every time. If I leave the key on and it cycles a few times, it seems to flood it. Hard start, hitting on a couple cyls after rolling over 15-20 times then starts.

So......fuel pump not putting out enough pressure/check ball not stopping it from draining back?
(Why is the injectors clicking every few seconds when the engine isn't running?)

Or something I'm overlooking?

Oh yeah, it's a '91 4.0 manual 4x4.
 


alwaysFlOoReD

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Have you tried starting it with the gas pedal fully depressed? That is the clear flooded engine mode. It shouldn'tstart or even try to start. If it does then you have leaking injectors.
 

Bracket racer

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Hmmmm, actually you just reminded me of two things. A couple times now it has felt hydro locked when I first hit the key in the morning. Half a roll then fetches up, let go of the key and hit it again and it rolls half a turn, pauses then rolls a few times and fires up. Doesn't seem to be gas in the oil though.

Second thing, if I turn the key on and off(checking fuel pressure) after 6-7 the motor gives a jump. It's firing one cyl (must be on compression of one of the cyls) I understand why it would spark, but not sure why the injector is firing.

Thanks for the reply, now I'll have to do more testing. Is this a common problem or just what it sounds like in this particular case?
 

Bracket racer

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Doing other stuff in the garage but walking by this morning noticed the fuel pressure is zero. Hit the key and it worked its way up to 30 psi but every time the injectors clicked, pressure dropped 5psi or so. Fired it up and held a steady 30psi. Idle is 1000 and it hunts from 750-1000. When the idle drops, the fuel pressure goes to 30, when the engine revs the pressure drops to 25 psi.

Anyway, just more observation.
 

alwaysFlOoReD

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30 psi is borderline. 40 is what you should see. Probably going bad pump.
 

RonD

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Do Clear Flooded Engine test that alwaysFlOoReD suggested in post #2
 

Bracket racer

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Socialist republic of Nova Scotia Canadastan
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1991
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Ranger supercab
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4.0 V6
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4.0
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Manual
2WD / 4WD
4WD
Total Lift
Crap load
Tire Size
35X12.5 (bald so I don't break parts)
My credo
Low range in Nova Scotia on YouTube!
I did and it works when it's flooded (key on engine off for a while)
But if I went out right now, the fuel pressure would be zero, it's been sitting for 4-5 hrs and I'd just hit the key and fire it up.

Sounds like a fuel pump problem so I'll look into it after the weekend.
 

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