Last week my 89 pickup (22RE) died on the road. In the couple weeks prior to this, it had been running almost as if it were missing, sort of studdering, while under constant throttle. Under load it seemed to be less noticeable but still there. Idle seemed normal though.

At this point, the truck will start fairly strong, run for 5-10 seconds as it slowly starts to chug and sputter then quit. I can barely keep it going sometimes by feathering the gas pedal, but pressing the pedal much at all just makes it stall.

I've been troubleshooting the fuel system, and while I haven't been able to actually test pressure yet, the pump seems to be working fine and the filter is new. I pulled the return line off the pressure regulator and jumpered the fuel pump test pins and I don't get any fuel coming out of the return of the pressure regulator - not a drop. I loosened the banjo bolt on the cold start injector and there seems to be good pressure there so I think the rail is getting good pressure.

Now there should be fuel running through the regulator and back to the tank, correct? If the pressure regulator is blocked or not working, would that keep the engine from running altogether?

Thanks in advance for any comments/suggestions.
- Chuck

Which line did you pull to check the fuel return? If the line on the top, that is vacuum and used to increase/decrease fuel pressure with the load on the engine.

No, I know the top one is vacuum and the bottom is the fuel return.

I just removed the regulator and I know there is pressure in the rail leading up to it because there was a pop and a nice splash of gas when I pulled it off.

Does there have to be a certain amount of pressure going into the regulator before it allows fuel to go through and back to the tank? I know the FSM states that you should hear fuel draining back when testing the fuel pump with the engine off.

At this point I'm trying to determine if it is the regulator or that the pump isn't pushing enough pressure...

The regulator works by bleeding fuel back to the tank that exceeds the pressure setting of the regulator (usually around 30-35psi depending on the vacuum on top of the FPR). So if pressure less than that, nothing goes back to the tank. With the FP test jumper in place and the ignition on, you should hear the pump running and the regulator operating will sound a bit like an air leak (hissing sound).

Yeah, I get absolutely nothing out of the regulator. I really need to get my hands on a pressure test kit to see what kind of pressure I'm actually getting on the rail.

I tapped the back end of the fuel rail for a fuel pressure sender:
- http://www.4crawler.com/4x4/CheapTricks/Gauges/index.shtml#Fuel/AirPressureGauge

Well I finally went and bought a fuel pressure test kit and found that while the pump was still working, it was only putting out about 15psi. I put a new pump in and she's back up and running now.

Funny thing though, I still don't hear fuel draining back to the tank through the pressure regulator like I'm supposed to when the Fp diagnostic jumper is used. And it is still doing that strange studdering thing that was happening prior to it quitting.

Little update - the condition is worsening, so much so that I can't trust that the truck will get me where I'm going anymore. While driving it is still exibiting the missing/studdering behavior (not really missing, as that would indicate a spark issue which I don't think this is at all). It has gotten worse so that now a couple times in the past couple days it suddenly bogged while driving and choked and sputtered but didn't completely die. Happened halfway to work this morning and I got off the side of the road and stopped. I smelled something which I think was the cat burning up fuel that dumped during a rich condition. I got a CEL for the first time as well this time but haven't had a chance to try to pull a code yet. The CEL went off after I started the truck back up and I was able to drive it home without it bogging again, though it was still running like crap.

I plan to pull the intake mani off this weekend and start picking everything apart: injectors (probably going to take 'em for cleaning/inspection), injector harnesses (I've never looked at that wiring but I know it is a common corrosion point), and fuel rail to check for any blockage.

I am very leary of the fact that no fuel is being recirculated out of the regulator outlet (regulator has been replaced) and I'm suspecting that whatever the reason for that is possibly what caused my old pump to fail. Could have burned up from backpressure maybe?

Anybody have any further ideas on what to look out for?

Probably wouldn't hurt to blow out the lines for crud. Might also check the fuel canister. Got a check valve in there, IIRC.

2 pumps same symptoms. It ain't the pump. Have you looked at what the voltage at the pump is? Possibly there is to much electrical resistance somewhere along the wires and connectors. Clean the connectors and use dielectric grease on em. I've started to see electrical corrosion problems on my '89 mini truck.

The thing I'd check is the mass airflow meter. I have an '89 with corrosion in the body of the MAF. The air measuring flapper likes to stick and was originally giving symptoms similar to what you mention. I need to pull it again and do something to keep the corrosion away.