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May I start a new post w/ this title? A week ago, as I was driving on a local highway, all of sudden I lost power. Suddenly, RPM was dropped to 400 and stepping on the accelerator pedal did not rev up the engine. And, as I was kept stepping (pumped a few times) on the accelerator pedal, engine rev'd up, but, soon RPM dropped to 400. I was able to drive a mile or so and I finally pulled into a small shopping center parking lot. There idling was very unstable w/ "Clicking" noise. RPM was going up and down between 400 and 1,100. Did not over heat. No CEL came on. So, I towed to my home after 2 hours of wait for a tow truck. Here are the pic's I took. Can someone tell me if FP Resistor going/gone bad, or, what would be a culprit of this problem? Car is running like "Nothing Happened" now. FP Relay I saw on the post (by Yamae) believe had a blue cap and the connector plugs were in a form of letter "T". As you can see mine is in yellow and 4 connector plugs, 2 in top and 2 in bottom. The first picture shows the exact location of FP Resister right underneath the MAF sensor. It was not in the trunk. Were Yamae's FP Relay and location of FP Resistor (in the trunk) for 94 LS400? This incident happened after approximately 40 miles of driving. I'm now carrying a jumper cable for FP+ and B connection in case same thing happens again. Should I check the FP itself? And, can someone tell me how I check this relay's resistance?
Yes, that's the fuel pump relay (yellow). I recently went through some debugging on my '91. Here's a post with a bunch of info that should help you debug yours.
At the end of it all, I had a soft-failing fuel pump. New pump and the car drives beautifully again.
Testing of the fuel pump relay is mainly done by applying voltage and seeing how quickly and reliably the relay is thrown. I think in my link I gave the resistance I measured, but there is not a spec for that as far as I know.
05-08-17, 04:40 PM
91 LS400 Fuel Pump Resistor
