Mechanics

FUEL PUMP, OR FUEL PRESSURE REGULATOR

1994 Ford Ranger • 200,000 miles

Ok, so my truck has been running pretty rough here lately, I have replaced the plugs and wires, mass air flow sensor, Ignition coil, and ran sea foam through it. My friend came over last night and hooked his computer up to it and we got 512 (Ithink) which I believe is No Codes In Memory. We also ran a fuel pressure test. The static pressure has me kind of puzzled. As soon as you turn the key on, the pressure jumped up to 35 psi but within a second, it drops to 6 psi. I believe the specs call for 35-45 psi (key on engine off) The fuel pressure is also a few pounds low while the engine is running too. With the engine running I am getting like 24-26 psi. I think the specs call for 30-40 psi here. (Key on engine running) Today I pulled the Fuel pressure regulator off, it was holding pressure to the fuel rail. The diaphragm is not leaking but I don't know if there is anything else to check on it, it is holding vacuum, and has good vacuum to it. Any suggestions would be helpful.
Thanks in advance
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Craig jaster
August 21, 2012.



Try a new fuelfilter. Your injectors may be leaking causing the low presure.

Hmac300
Aug 21, 2012.
The fuel filter was recently replaced. I have also pulled the tank, flushed it and cleaned the sock.
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Tiny
Craig jaster
Aug 21, 2012.
Engine runing fuel pressure is 28-45 sounds like your pressure is low.

Hmac300
Aug 22, 2012.
Yea I googled the pressure specs last night and got a result of 35-45psi while running and 30-40psi static but that might be wronge im gonna do some more research

Tiny
Craig jaster
Aug 22, 2012.
The fuel filter has no efficiency on inj. Bleed off. Cycle the key 8-10 times, waiting for the pressure to bleed off. DO NOT turn the engine over while cycling the pump. Then simply pull the spark plugs and look for one that is fuel saturated. That hole is your leaking injector. Disable the ign. System and spin the engine over, prior to re-installing the plugs. This will prevent bad things from happening when you restart it. Hope this helps, Doc

DocDTC
Aug 22, 2012.
Ok will check that out tomorrow
about the low fuel pressure, and loss of power, will a leaking injector cause both symptoms together?

Tiny
Craig jaster
Aug 22, 2012.
In a nutshell, yes. I could tell you how to confirm it with a scanner using mode 6 data. But I'm thinking you probably don't really have those kind of tools just lying around. I bet your mileage has dropped way off, and the exhaust is probably really warm, both at the tailpipe and at the cat. Converters. But I bet it starts great when cold but harder when its warm, am I getting close? Let me know, Doc

DocDTC
Aug 22, 2012.
Well Doc, you're real close, it always starts up great, but yes, it runs worse under higher ambient temperatures. After the engine warms up, it does get better. When the engine is cold, I have to pretty much floor it when pulling away from a light. It does better at higher rpms than if I would pull away from a stop normally. I have noticed some carbon buildup on the outside of the bed above the tail pipe. It actually doesn't have any cats on it. They were removed before I got it.

Tiny
Craig jaster
Aug 22, 2012.
Sounds like an open injector to me. If nthe O2 sensors still are reading O2 content, every time a cylinder misses, the sensor see alot of oxygen and tells the ECM that the motor is running lean, so it adds more fuel. Making the problem only get worse. Try the plug thing and let me know. Doc

DocDTC
Aug 22, 2012.
OK Doc, so I did the plug thing, cycled the key about 30 times then pulled all six plugs. None are wet although they are brand new, four out of six have a light white burn to them while the back plug on both sides look new besides a little black carbon on the couple threads that stick through the bottom of the heads. So unless I'm doing the test wrong, I dont have a leaky injector. What would be my next step?

Tiny
Craig jaster
Aug 23, 2012.
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