Question about 2001 Buick Century

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85 century fuel pump will not activate when key is turned on. power to pump if you crank on engine. also doesn't seem to get power to relay when key is on. only has power when cranking. put in new relay and new ignition switch

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Crank sensor i bet it can cause lots of problems

Posted on Oct 04, 2009

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1 Answer

Why is fuel pump relay getting no power?


The fuel pump relay has B+ voltage on pin 87 at all times , Pin 85 has B+ voltage only when cranking engine or for first two seconds from key on .( to prime fuel system) .Watch this youtube video ( how to test GM fuel pump circuit ) GM Fuel Pump Relay Testing

Mar 31, 2016 | 1995 Buick Regal

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When i turn the key the engine cranks over but does not start, if i continue to crank it for a minute or two then it will eventually start and drive just fine. any ideas?


This sounds like a fuel system priming issue. When you first turn the key to the ON position (not cranking yet), you should hear a three-to-five second buzzing noise. This is the fuel pump running to pressurize the fuel system for cranking. This is controlled by the PCM and is relay activated. Once the vehicle starts and oil pressure rises, then the fuel pump is activated by the PCM via a different relay. If you can't start at first, what is probably happening is that the prime is not occurring and you have to crank it until the PCM sees oil pressure and then fires off the fuel pump. It could be PCM wiring or a bad fuel pump prime relay.

Oct 02, 2015 | Cars & Trucks

1 Answer

I installed a fule pump and started right up, and then stopped runing again, I was going to clean fuel filter, and fuel kept flowing throuule the fuel line. I changed fuel pump relay five times, I...


Maybe the oil pressure sensor or switch that keeps the pump running after engine started.

If you jumped 87 and 30, it should have turned the pump on. If those are the right terminals at the fuel pump relay, and I think they are. Those are usually the right ones.
Try this: one of those terminals should be hot at all times, the feed for the fuel pump. Check for a hot terminal there. If the feed for the pump is lost, it will probably be a blown maxi fuse or fusible link supplying that relay's power feed.
If it still starts and dies, check the fuel pressure. If pressure is at specification, both key on, engine off and with engine running, it could be an ignition problem (crank sensor?), not a fuel problem. But you may be right to pursue the oil pressure switch or the pcm, if the pump was still running as you say at the fuel filter .

At terminals 85 and 86 of the pump relay, you could check for the computer signal on one of those with the engine cranking. With engine cranking, the computer sends a signal to the coil side of the relay, either the 85 or 86 terminal, and the other terminal will go to ground. Do you have a test light or voltmeter?

Apr 26, 2014 | 2002 GMC Sonoma Extended Cab

2 Answers

No power to fuel pump on 92 olds silhoutte


The oil pressure sensor only keeps the pump running after the vehicle is started. If you turn key to on, the computer should signal to the fuel pump relay, turning the pump on for a couple of seconds to pressurize the fuel system. Then the computer signal stops. When the key is turned to start-cranking the engine- the computer again energizes the fuel pump relay, keeping the pump running until the engine starts.
If you have a voltmeter or test light, pull the relay out and check the relay terminals. One should be hot at all times-the power feed for the pump. The computer signal will be on the coil side of the relay-will have power for 2 or 3 seconds after key is turned to on. Or it will have a constant signal when the engine is cranking. If you can find both hot terminals at the relay, then start looking for a bad wire from relay to pump, or a bad ground for the pump, or a bad ground for the relay's coil side. Post back if unclear or other questions. When you pull the relay out, the diagram for it will be on the side of the relay-telling you which is the power feed and the terminal to the pump, and the coil side of relay, both the coil power side and the coil ground terminal.

Jan 16, 2014 | Oldsmobile Silhouette Cars & Trucks

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Put $20 in gas in 2002 Dodge Durango night before last. Drove fine for 25 miles but when I was going down a bridge, I felt the engine stop. Still had all interior power, but no power steering. Tried to...


Check for fuel pump when u turn on key it should prime for 5 seconds. Then it could aslo be a crank sensor or cam sensor more info need . May be even a timing belt check compression

Oct 28, 2013 | 2002 Dodge Durango

1 Answer

1999 Ford Explorer Sport Starting Issue


It sounds like the pump is failing. That or sometimes not getting electricity. To check which it is, you could use a voltmeter or test light at the gas tank's electrical plug in. You need to check for power on the fuel pump wire when the engine is being cranked for starting. Do this when turning the key to on does not cause the pump to turn on for 2 seconds as it should. The fuel pump has power for those 2 seconds when key is turned to on, and again has power when the engine is cranked. You might miss the two second signal, so check for power when car won't start-when pump won't turn on-and with the engine cranking. If you have a signal then and still no pump coming on, then you must have a failing pump.
But if you have NO power to fuel pump wire with engine cranking, then it is a problem elsewhere-probably the pump relay (try a new relay if you haven't already). That relay is signaled by the engine computer when key is turned to on or when engine cranks . so you could do some testing at the relay if needed.

Mar 04, 2017 | 1999 Ford Explorer

2 Answers

Escort won't start when cold and has the strangest solution...


no, not likely. And a dry hose is a good sign, but a hose wet with gas is a sure sign of a failed pressure regulator. Your problem may be the pump not priming the fuel system. Here's how it is supposed to work: when you turn the key to on, computer will signal the fuel pump relay to turn on for about two seconds, and without a cranking signal from the engine, computer will then turn the pump off. When key is turned to crank, the computer will then turn pump back on-when engine is cranking or running, the pump is on continuously. But just turning the key to on, you should hear the pump run for about two seconds, and that will pressurize the fuel system.
At those times when it doesn't want to start, you should test the fuel pressure to see if the fuel rail is pressurized. If no pressure or low pressure, diagnose the wiring at the fuel pump relay. The relay is very simple- 4 prongs, 2 on the power side, and 2 on the coil side. The power side has a hot at all times wire and then the wire going to the pump. The coil side of the relay has a wire from the engine computer, and the other coil side wire is a ground. When the coil side is energtized by the wire from the computer, the relay is switched on and will pass power from the hot wire to the pump. So if the pump doesn't come on briefly to prime the system, the computer may not be signalling the relay, or there is a wiring problem around the relay. Good luck. You might just try a different relay-maybe yours is sticky and not responding.

Oct 29, 2012 | Cars & Trucks

1 Answer

Does the fuel pump relay work the ignition power to the fuel pump i have no power to the fuel pump when ignition is on but power when cranking the engine over


Most cars are designed to only put power to the pump for a few seconds till the rpms reach a certain point so it doesn't keep pumping if engine stops. If you have power while cranking and you didn't have someone turn key on and watch test light right away you could have not noticed having power with key on and you probably have a bad pump. Also did you check to see if you had good ground in plug also? I would say if you have power and ground at plug pump is bad.

May 24, 2012 | Scion TC Cars & Trucks

2 Answers

I have a 98 jimmy.4dr, 4wd..problem --no power to fuel pump....if you stand on drivers side looking at fuse panel (the top right pin of the relay has power, but thats the only one...if i jump power to the...


Fuel Pump Electrical Circuit
OPERATION
When the key is turned ON with out the engine running, the control module turns a fuel pump relay ON for two seconds. This builds up fuel pressure quickly. If the engine is not started within two seconds, the control module shuts the fuel pump OFF and waits until the engine starts. As soon as the engine is cranked, the control module turns the relay ON and runs the fuel pump.
When the engine is cranking or running, the control module receives the Crankshaft Position (CKP) sensor reference pulses which in turn energize the fuel injectors. As a back-up system to the fuel pump relay, the fuel pump can also be turned ON by a fuel pump oil pressure switch. When the
engine reaches about 28 kPa (4 psi), and the fuel pump relay does not complete the circuit, the fuel pump oil pressure switch will close to complete the circuit to run the fuel pump.

An inoperative fuel pump relay can result in long cranking times, particularly if the engine is cold. The fuel pump oil pressure switch will turn ON the fuel pump as soon as oil pressure reaches about 28 kPa (4 psi).



You can test to see if the relay it's self is bad by swapping it temporarily with another relay. If your truck has AC then that one should be compatible. Just compare the two to see if they're the same and if so, try using the AC's relay.

Apr 05, 2011 | GMC Jimmy Cars & Trucks

1 Answer

Turn key, cranks but no fuel still after new pump.


every key cycle(5 secs appart) will turn pump on for 3 seconds.This is done to insure pressure at the injector when cranking,otherwise hard starting would insue.The engine computer drives a relay in the underhood junction box which sends 12 volts to the pump.An audible click of that relay and the pump can be heard key on/engine off for 3 secs via the ignition signal to the ecm which drives the fuel pump relay.

Jul 16, 2009 | 2000 Chevrolet Cavalier

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