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1990 Buick Century W/3.3 won't run/start after reaching operating temp., no fuel pressure at rail

stumped59stumped59 Posts: 4
edited April 5 in Buick

Have 1990 Buick Century w/3.3 engine (78000 miles) First sign was it cut out at highway speed (65) picked back up w/no problem for a few days. Got to work one night, killed engine, wanted to move, but would not start, next morning started up w/no problem. Stopped to get gas, it would not start, after a few trys it started. Got home, when time for work, started fine. About 12 miles down the road started cutting out and finally quit, no fuel pressure at rail. Towed to shop, would start but not accelerate. After checking had a bad Ignition Control Module, installed new one. It cranked right up, let it warm a couple a mins. accelerated, did great, thought alright, fixed. Was running while putting tools up, then died, would not restart, no fuel pressure at rail. Could not hear fuel pump, installed new one as well as inline filter. Same thing will start good, run good until reaches operating temp. and may die or stall in gear...will not restart, still no fuel pressure at rail. Have spark, can spray starting fluid in intake and it will run. What would stop power to new (OE) fuel pump so it won't come on? Really would appreciate any ideas on this.

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Answers

  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,657

    I think if I remember correctly that your fuel pump circuit is tied into your oil pressure sensor--so I'd look at that sensor as a possible culprit.

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  • stumped59stumped59 Posts: 4
    edited April 7

    MrShift you are right and Thank you for your response. By research I have done the Fuel Pump Relay and the Oil Pressure Sensor operate parallel to each other and have been told by others that might be a possible culprit, but have also read that the Oil Pressure Sensor or and asking for as many opinions as I can get. The Oil Pressure Sensor works when oil pressure hits approx. 5 - 10 lbs. If I understand correctly, at cranking of engine it is in Open loop and goes to Closed loop (Computer Control) at engine operating temp. is reached. Does that mean that basically that in Open Loop that Fuel Pump Relay is in control of Fuel Pump and when the engine reaches temps. Computer goes to Closed Loop then the Oil Pressure Sensor takes control (and drops fuel pump relay) and that if it is bad that is why it shuts off the fuel pump because the Computer is not reading any signal from the sensor because it was not intended to shut engine down just for low oil pressure? I ask because I saw a video that if relay or sensor did not work the other one would to supply power to fuel pump. Or is that just during the cranking of the engine?

  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 18,460
    edited April 11

    @stumped59 said: MrShift you are right and Thank you for your response. By research I have done the Fuel Pump Relay and the Oil Pressure Sensor operate parallel to each other

    I think you need to do some voltage checking. If this is consistent that it dies when warmed up that will help. But you need to find the connector for the fuel pump leads near the fuel pump and test there for voltage and for ground. It will help if you know the colors for the pump motor power and ground and for the leads to the fuel level sender.

    This is a Buick for which I don't have a service manual for anything similar.

    But first, when it dies, what happens when you turn the key OFF and then back ON? Do you hear the fuel pump run for a second or two as it does the priming cycle?

    If not, that's a hint. You need to have the car up on secure jackstands and have the leads located at the rear so that you can probe them near the fuel tank connection. You'll need to have your ground lead from the meter touching something definitely grounded. If the engine dies, leave the key ON. But I'd check it while it's running for power to the lead (which may be red or orange) and also check that the black lead, which I hope is the ground for the fuel pump, is grounded. Then when it dies check again for a 0 ohm resistance on the ground and 12 v for the power line before the key is ever turned off. That will diagnose whether you're losing power to the fuel pump or the fuel pump itself is quitting.

    I'll have to do some checking on my 1993 manual for a leSabre, which may be similar to your car. But I'd pay special attention to the ground. A Cincinnati car technician who did a radio call in show for auto repair always said anytime something electrical happening didn't make sense, check the grounding first.

    I believe on my leSabre there was a relay (on the right front passenger side below the dash in a relay and fuse center and that was for the fuel pump. I wonder if a relay could be heating up after time and opening up. This would be the relay operated by the key ON signal for fuel pump below 400 rpm IIRC and for the oil pressure that keeps the fuel pump running until an accident stops the engine.

  • stumped59stumped59 Posts: 4
    edited April 19

    @imidazol97, Thanks for your reply. I went ahead & changed the Oil Pressure Switch as MrShift said. It cranks & runs as it did, but it now stays cranked after reaching operating temps. After installing new switch I let it run, killed it, then it started right back up several times. Seems like it had a slight miss to it so throttled it up...kinda missed & as I throttled up a little more went into a surge like I was throttling up & down. Started unplugging injector connectors...at the third one (only that one) the engine stopped surging, plug it back up & it surges. Also have a strong smell at tailpipe, very rich, and pipe is very black with soot. Also small amount of white smoke from tailpipe (unplugged injector...it stopped smoking) and the engine light has been on & trouble code is rich fuel. Found out those are classic signs of excess fuel dumped into the system. I just a few days ago found out from a youtube video by @scannerdanner that system is designed to shut down fuel pump in that situation "when" it reaches operating temp. which is when it goes into closed loop (Computer Control). My thinking is that the fuel injector has been going bad (by dumping excess fuel), when it got bad enough it system shut engine down. In all our atempts to contiueously try to crank engine the ICM & OPS was probably old/weak, it finished them off, once I had it running long enough I may have found the "real/intitial" root of the problem, "bad fuel injector". One other note I might mention, this vehicle MAY have had 300 miles a year put on it for last 2/3 years. Would still like any & all opinions on things to keep me in right direction or close at least. Planning on changing injectors one day this coming week. Finially going to have some nice weather around here maybe. Thanks to any & all help.

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