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View Full Version : Is your SC running BAD? Fuel pressure regulator?



unrapit
06-19-2011, 11:25 AM
Hello All,
My 1992 SC has been running bad! Chugging backfiring Very hard to start when it gets warm. Acts like its missing when you step down on it.I changed crank and cam sensors changed the ignition module every dam sensor you could replace and the plugs and wires.Had the fuel pressure checked it was fine. Runs fine at an idle. Yesterday i said screw it and i started looking for vac leaks and electrical problems.I took the super charger off and the tupe that bolts to the intake.I was checking my wiring and seen the little can on the fuel rail.I believe its a fuel regulator.I have another fuel rail with the can on it so I changed that.Didnt find no wiring issues or vac leaks so i put it back together and went for a ride.I have no more issues car has never ran better! Hope this helps someone with the same issues!

David Neibert
06-19-2011, 11:55 AM
Hello All,
My 1992 SC has been running bad! Chugging backfiring Very hard to start when it gets warm. Acts like its missing when you step down on it.I changed crank and cam sensors changed the ignition module every dam sensor you could replace and the plugs and wires.Had the fuel pressure checked it was fine. Runs fine at an idle. Yesterday i said screw it and i started looking for vac leaks and electrical problems.I took the super charger off and the tupe that bolts to the intake.I was checking my wiring and seen the little can on the fuel rail.I believe its a fuel regulator.I have another fuel rail with the can on it so I changed that.Didnt find no wiring issues or vac leaks so i put it back together and went for a ride.I have no more issues car has never ran better! Hope this helps someone with the same issues!

Sounds like the old regulator had a bad diaphram that was allowing fuel to leak into the vacuum hose and into the intake manifold.Had the same thing happen on my 91 SC a long time ago. Took me nearly a year to figure out what was happening.

David

supertodd
06-19-2011, 07:57 PM
I am having very similar issues with my 90sc and was thinking about the fuel pressure regulator but I had no idea where it was on these cars. How hard was it to get at? How long did it take you?

JeepsterSC
06-19-2011, 09:23 PM
The fuel pressure regulator is under the cowel, behind the return plenum on the fuel rail, above the driver's side head. You will have to remove the supercharger and the retrun plenum to access it. You will also need to take the fuel rail loose, as the regualor bolt heads are on the bottom of the fuel rail. The fuel rail has 4 torx head bolts on the intake manifold and a very tricky bolt behind the driver's side head(the bolt screws into the head between the head and the firewall) that takes either a 10 mm or 13 mm socket. 89-93 SC's take a 3 bolt hole regulator and 94-95's have 2 bolt holes.

This may be an oppertune time to replace the plastic tubes on your fuel rail per this article

http://www.tccoa.com/articles/mn12how-to/fuel-rail/fuel-rail.html

T/A Turbo 1989
06-19-2011, 09:31 PM
My '89's both are having issues when it's hot or I've taken on a long trip.
Some of the above mentioned issues are happening. As well, feels like the fuel is vapor locking or boiling by the time it gets to the engine.
Car stumbles, runs ~~~~~~, powerless and even dies and is hard to restart until it cools.
I have noticed on my '89 Automatic that when I put a fresh fill of fuel in the tank to top it off that often times cures the problem. So that's what got me thinking that the fuel was getting too hot in the tank or before it's getting to the injectors.
I guess I just want to verify that the problems I've had above will be fixed by replacing the fuel regulator. Since it's going to be a decent amount of labor to do it, I didn't want to go to all that work and not fix the issues I'm having.
I agree it's got to be a fuel issue and the regulator does sound like the fix...

David Neibert
06-19-2011, 10:56 PM
My '89's both are having issues when it's hot or I've taken on a long trip.
Some of the above mentioned issues are happening. As well, feels like the fuel is vapor locking or boiling by the time it gets to the engine.
Car stumbles, runs ~~~~~~, powerless and even dies and is hard to restart until it cools.
I have noticed on my '89 Automatic that when I put a fresh fill of fuel in the tank to top it off that often times cures the problem. So that's what got me thinking that the fuel was getting too hot in the tank or before it's getting to the injectors.
I guess I just want to verify that the problems I've had above will be fixed by replacing the fuel regulator. Since it's going to be a decent amount of labor to do it, I didn't want to go to all that work and not fix the issues I'm having.
I agree it's got to be a fuel issue and the regulator does sound like the fix...

Before changing the regulator, do a pressure test. You can rent or purchase a fuel pressure test kit at AutoZone or other places that attaches to the shrader valve on the fuel rail. With a fully charged battery you should get 38-40 psi with key on engine off, and it should hold pressure for 10 or 15 minutes and slowly bleed off to nothing in about 30 minutes. If it bleeds off quickly (like dropping to 25 psi as soon as the fuel pump stops) you could have an injector that is stuck open (very common)or a bad diaphram in the regulator. Pulling the vacuum hose off the regulator and checking for fuel in the hose is the easiest way to check the regulator for internal leaks. To check for a leaking injector you have to pull the fuel rail off the manifold and put the rail under pressure to look for leaks. Regulator can also be bad without leaking fuel, but that would be rare.

With the motor running the vacuum hose on the regulator is what controls fuel pressure. At 20 inches of vacuum you should see about 35 psi, with zero vacuum 38-40 psi and under boost fuel pressure should increase one pound for each pound of boost. If you have 40 psi at zero vacuum/boost you should have 50 psi at 10 pounds of boost. If the vacuum hose breaks or falls off the regulator the motor will run rich while in vacuum and lean under boost.

David