my sons 86 2.8 sport coup is a project we ha re done it. it has been running good the other day he come out from school to find that the fuel pump wasnt working we put a new one in about three months ago. it sat for about a week and i had him put in a bottle of heat on a friday on monday after school it started. i told him to drive it home. he went 2 miles and stoped for gas and it failed to start again he waited about 15 min andit started again. it went about 3miles and quit again and never started again. we towed it home. I checked fues by batery its good. the relay is good. I put a test light to plug at tank and it looked week. i will be putting a meeter on it to test voltage. any one have an Idea what this could be. I was thinking fuel pump but now not sure.

 

Have you ohmed the injectors to make sure they're good? Is the fuel filter new or old? A cloged filter will cause issues. Get a fuel pressure gauge and check your fuel pressure on the rail.

 

yes injectors are all good it is and we put in a new filter. as for pressure if we turn on the key and can hear the pump it will run if we dont hear thwe pump it doesnt run. so im thinking that there is something causing it to not get power or the pump is defective. if it was easy to change the pump i would just do that. how about ohming the pump does anyone know what the pump should ohm??

 

How the pump ohm tests will depend on the position of the brushes on the commutator. Between 2 ohms and 5 ohms I would guess. It is more likely that you have a power supply issue to the pump or a poor ground. Ground connections are often overlooked.

You need to have a good wiring diagram of the system and know how to read it. Follow the flow of power from the pump back to the battery and wiggle each connection and section of the harness while a helper holds a test light to the pump circuit of the connector at the tank.

I have had issues with the connector at the relay. Also, the oil pressure fuel pump switch and its connector could be an issue. From the sounds of your trouble, I would think a wiggle test of the wiring and connectors should reveal the problem. It is common for the female terminals of the connector to lose tension over time and make poor contact with the male terminals of the switch or relay. Look for signs that the plastic connector body has been hot. High resistance in a connection, especially in a high load circuit like the fuel pump, will often cause heat and deform the plastic.

Did you replace the pump yourselves or have it done? If you did do it, did you verify good wiring and connections inside the tank at the sending unit?

Something to remember also is that the ECM turns on the pump when the key is turned on for about 2 seconds, then waits for a signal from the distributor before it turns the pump back on. However, the ECM has a decay timer and will only turn the pump on with key on once or twice in so many minutes. Don't expect the pump to run every time you turn the key on. One other thing to check is the CRANK fuse in the fuse panel. Poor contact at this fuse could cause a symptom like you're seeing.