Vac and fuel pressure specs
04-19-2015, 01:34 PM
#1
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Thread Starter
Vac and fuel pressure specs
86 f150 302. Have hesitation issues.
Replaced intake manifold gasket, and a number of vac lines. Reading 18" at idle, seems a little low. Under light throttle is rises a bit. Under heavy throttle it drops to about 5".
Fuel pressure at the rail is 25-30 psi, almost hits 40 under throttle. Definitely low I think. The fpr is shiny and not leaking. Will a dead in-tank pump cause the hp to under deliver?
Also it's been fully converted to single tank. No more switching reservoir or selector switch. Also there is no fuel filter (I'm discovering how lazy the PO was. No idea why it was removed, but as far as pressure goes, there's no filter to change...)
Replaced intake manifold gasket, and a number of vac lines. Reading 18" at idle, seems a little low. Under light throttle is rises a bit. Under heavy throttle it drops to about 5".
Fuel pressure at the rail is 25-30 psi, almost hits 40 under throttle. Definitely low I think. The fpr is shiny and not leaking. Will a dead in-tank pump cause the hp to under deliver?
Also it's been fully converted to single tank. No more switching reservoir or selector switch. Also there is no fuel filter (I'm discovering how lazy the PO was. No idea why it was removed, but as far as pressure goes, there's no filter to change...)
04-19-2015, 04:19 PM
#2
Member
Thread Starter
It seems pre 88 there was only the reservoir filter and no in line? Spec for this engine is 30-45 psi idle & running. Below 30 would indicate a fuel supply problem I assume. Can't hear the in tank running.
Also, the hp sort of whines when the engine slows down, not sure what's causing what...
Also, the hp sort of whines when the engine slows down, not sure what's causing what...
04-19-2015, 06:50 PM
#3
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Thread Starter
After I pulled off the pressure gauge, the fitting was all full of coffee grinds. Likely the injectors are clogged as well I imagine. I just had the intake off a couple weeks ago too. Looks like I'll have to pull it again to get the rails off?
Is there an ideal place to throw on an in line filter? I know subarus have them right on top of the engine for extra convenience. Would it be better before or after the high pressure pump? Or on the firewall behind the intake?
Is there an ideal place to throw on an in line filter? I know subarus have them right on top of the engine for extra convenience. Would it be better before or after the high pressure pump? Or on the firewall behind the intake?
04-19-2015, 10:11 PM
#4
Better before the pump, to protect it.
Your truck will run between 30 to 45, which means below 30 it won't run at all. Low to mid 30's is a problem.
You should be looking at 42-43 psi KOEO. Should drop to high 30's at idle and climb back up to max as you open the throttle.
Vacuum is low. Either a vac leak or a wrong cam most likely. Lots of people shove mustang cams in trucks thinking it's a good idea.
Your truck will run between 30 to 45, which means below 30 it won't run at all. Low to mid 30's is a problem.
You should be looking at 42-43 psi KOEO. Should drop to high 30's at idle and climb back up to max as you open the throttle.
Vacuum is low. Either a vac leak or a wrong cam most likely. Lots of people shove mustang cams in trucks thinking it's a good idea.
04-19-2015, 10:20 PM
#5
Member
Thread Starter
Thanks Chris, I'm going to ignore the possibility of the wrong cam for now! I know not the history other than what I've discovered so far.
Planning on installing a filter and pulling the injectors tomorrow. I'll post an update after.
Planning on installing a filter and pulling the injectors tomorrow. I'll post an update after.