'92 has pulsating fuel pressure
Thread Starter
Instructor
Joined: Jun 2012
Posts: 111
Likes: 1
From: Mariposa, CA
'92 has pulsating fuel pressure
When I turn the key on I hear the fuel pump start up but within 5 seconds I hear a pressure pulsation in the fuel lines under the hood.
And I can feel the pulsation around the pressure regulator. The Service Engine light flashes with the pulsation. Car will start but runs
with erratic idle. I'm thinking regulator. It looks original. What else could it be ? Fuel pump pulsator ?
Thanks....
And I can feel the pulsation around the pressure regulator. The Service Engine light flashes with the pulsation. Car will start but runs
with erratic idle. I'm thinking regulator. It looks original. What else could it be ? Fuel pump pulsator ?
Thanks....
Melting Slicks
Joined: May 2003
Posts: 2,076
Likes: 281
From: Dyersburg TN
putting a fuel pressure gage on fail should be very telling. I am assuming you start the car since the pump will shut off after priming if you just do key on and do not crank. Pump and pulsator control pressure to the regulator. Are the vacuum lines to the regulator good condition and connected?
Thread Starter
Instructor
Joined: Jun 2012
Posts: 111
Likes: 1
From: Mariposa, CA
Fuel pressure pulsating 42 to 46 psi with ignition key ON
I replaced the fuel pressure regulator since it looked like the original one and I wanted to rule that out. Vacuum line to it looks fine.
However, the condition did not go away. With the ignition key in the "on" position, not even going to start the engine, I hear a pulsating sound in the fuel line
and the pump sounds like it is cycling on and off and as it does that the "Check Engine Soon" light on the dash is cycling on and off with it.
I have a pressure gauge on the fuel rail and the reading cycles between 42 and 46 psi with the ignition key at the "on" position. The engine will only start if I give it part throttle and will not idle.
Black smoke at the exhaust results. With the engine turned off the fuel pressure drops to 30 psi in about 60 minutes.
Not sure what to check next. Fuel pump relay? Pump? Check valve?
However, the condition did not go away. With the ignition key in the "on" position, not even going to start the engine, I hear a pulsating sound in the fuel line
and the pump sounds like it is cycling on and off and as it does that the "Check Engine Soon" light on the dash is cycling on and off with it.
I have a pressure gauge on the fuel rail and the reading cycles between 42 and 46 psi with the ignition key at the "on" position. The engine will only start if I give it part throttle and will not idle.
Black smoke at the exhaust results. With the engine turned off the fuel pressure drops to 30 psi in about 60 minutes.
Not sure what to check next. Fuel pump relay? Pump? Check valve?
Thread Starter
Instructor
Joined: Jun 2012
Posts: 111
Likes: 1
From: Mariposa, CA
This is a new condition. Check engine light does flash with the pulsation of the fuel pressure. Nothing had been worked on prior to this condition developing. Car has sat in the garage for several months.
Ran fine before that.
The timing of the 42 to 46 to 42 psi is about 2 to 3 seconds. If I leave the key in the "on" position it will keep cycling.
There is no aftermarket car alarm.
I will check that C12 voltage.
Thanks...
Ran fine before that.
The timing of the 42 to 46 to 42 psi is about 2 to 3 seconds. If I leave the key in the "on" position it will keep cycling.
There is no aftermarket car alarm.
I will check that C12 voltage.
Thanks...
Pro
Joined: Sep 2019
Posts: 716
Likes: 135
From: Buchanan, Michigan
Did you check/replace the pulse damper and hoses going from the in tank pump to the steel line on the hanger? Next step would be verify the fuel pressure regulator under the hood isn't bad, and the fuel filter on the frame rail below the passengers feet is good. If all that checks out then start diving into the pump, relay, and maybe wiring. These cars are old, corroded connections, poor grounds, pooy executed fuel pump repairs in the past, sticky injectors. All could cause pulsating fuel pressure. Cover the basics first.
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