Mechanics

FUEL PUMP, OR FUEL PRESSURE REGULATOR

1994 Ford Ranger • 200,000 miles

So this is the second time I have posted on this topic. I have run through all the previously suggested tests and I'm still having the same problem. I have replaced the fuel pump, only to find that I wasted $75.00. I did come acrossed an issue that I could see would cause a fuel pressure issue. The hose that connects the pump to the sending unit was split down the side and basically shooting gasoline back down into the tank. Attached is a pic of what I removed and replaced. I'm pretty sure the pump is still good but I replaced it anyways because with the hose like that I simply dont know how long that pump has been over working itself. With the new fuel pump, I still only get 26psi running pressure, but the static pressure is holding at about 36 pis(key on engine off)
The diaphragm on the fuel pressure regulator seams to be holding a vacuum well, and isnt leaking any fuel. The injectors dont seam to be leaking off per the test I ran. I have a timing light that I'm going to hook up to it and replace the fuel filter again. Any other suggestions would be helpful.
Thanks.
Avatar
Craig jaster
August 26, 2012.




The regulator is fine. When you decrease manifold vacuum, the pressure increases.

The pressure is on the low side. I like to see around 35 at idle with the vacuum line on the regulator

Roy

ASEMaster6371
Aug 26, 2012.
Ok, I took it for a test drive and its still bogging down under a load, not as bad but still is. When you throttle the engine doesnt that give you more vacuum?
The pump should be more than enough to provide adequate pressure to the rail. The specs on the pump call for minimum of 80 psi and max 100 psi. Unless I got a bad pump which has happened before.
AD

Tiny
Craig jaster
Aug 26, 2012.
No, less vacuum under load. Yes, you could have a bad new pump. Airtex is a good pump but you never know.

Roy

ASEMaster6371
Aug 26, 2012.
Regardless of the rpms of the engine, an electronic fuel pump is going to continuously give you the same pressure, and the regulator is going to adjust the pressure into spec right?

Tiny
Craig jaster
Aug 26, 2012.
The only things on the fuel system that arent new as of today are injectors, fuel rail, lines and filter. The filter is the only thing left that would cause loss of fuel pressure

Tiny
Craig jaster
Aug 26, 2012.
Nope, wont do it. There is a bypass if the filter gets clogged.

Roy

ASEMaster6371
Aug 26, 2012.
Ok, so less manifold vacuum increases the fuel pressure right, so does that mean I have too much manifold vacuum at idle?
How does manifold vacuum get too high there are any vacuum regulators anywhere, I cant find any. Could that mean I have a vacuum clogged somewhere? An open vacuum line would reduce vacuum elsewhere or could my idle be set too high? Im stumped here. Could the throttle position sensor cause this?

Tiny
Craig jaster
Aug 26, 2012.
You vacuum is fine, your regulator is fine. There is no vacuum issue. It is a pressure issue possibly from a weak new pump.
Roy

ASEMaster6371
Aug 26, 2012.

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