Fuel pump not turning on without several key turns

[usera]

I started experiencing random issues where my fuel pump wouldn’t turn on after turning the key to position III, several attempts would get it to kick in so I swapped the pump, the relay and inspected the cabling but nothing has fixed the issue.

I am running TEC3r and the motor is a 30-3.2SS.

Looking for advice on what to troubleshoot.


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[dreichman]

Maybe the ignition switch.

[mrrolleyes]

Maybe the relay.

Take it out and short the circuit and have someone turn the key.

[usera]

Thanks for the replies, I have swapped the relay and the issue remains consistent. I am going to jumper the relay regardless to be sure.

The ignition will always turn the engine over, it just doesn't kick over the fuel pump, does that rule the switch out?

[lsf911]

It could be your fuel pump. Have you applied power to it directly?

[fanaudical]

Is the fuel pump relay activated by the the TEC3R CPU? If so, are you sure the relay is being triggered?

[dreichman]

Originally Posted by usera

Thanks for the replies, I have swapped the relay and the issue remains consistent. I am going to jumper the relay regardless to be sure.

The ignition will always turn the engine over, it just doesn't kick over the fuel pump, does that rule the switch out?

It does not. Several separate circuits run through the switch.

[Quicksilver]

Grab a meter and see what voltage you have a different points when you have the issue.

[Guardsred911]

there are a couple plugs and harnesses on the backside of the Airbox that can come loose. And a number of plugs in the engine bay that should be checked for tightness/connectivity... good luck!

[boyt911sc]

Originally Posted by usera

I started experiencing random issues where my fuel pump wouldn’t turn on after turning the key to position III, several attempts would get it to kick in so I swapped the pump, the relay and inspected the cabling but nothing has fixed the issue.

I am running TEC3r and the motor is a 30-3.2SS.

Looking for advice on what to troubleshoot.


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Usera,

What model year is the car/chassis? It is quite difficult to give you a good advise without knowing the car/chassis. While the electrical systems remained similar, they are slightly different from model year to model year.

Tony

[MichaelSJackson]

Shot in the dark...

My relay socket was tired and worn, causing the connection to be flaky. The tech took a knife and splayed open the prongs on the relay. Problem solved.

If you look at the prong ends, you'll notice they are covered with a thin sheet of metal and there is a cross or 'X' on the ends. Put a knife edge in the seem and work it a little to expand the end just a little.

Probably not your problem, but cheap and easy to try.

You can also remove the relay and just jumper the power direct to the pump. That will tell you if the problem is on the pump side or the switch side.

[usera]

Originally Posted by boyt911sc

Usera,

What model year is the car/chassis? It is quite difficult to give you a good advise without knowing the car/chassis. While the electrical systems remained similar, they are slightly different from model year to model year.

Tony

The car started life as a 1978 SC, the 3.0 was built to 3.2 and several hands have been in it so makes troubleshooting way more complicated. I really appreciate everyones help on this.

I'll recap: I started to notice that the pump would not come on when I turned the key to position III. Moving the key back to position I then to III several times would eventually get it to come on. I have swapped the Relay and Pump but the same issue remains. I am going to look at the ignition switch and jumper the relay this afternoon. As far as the TEC3r question, I have no idea if that is what actuates the pump so I will read up on that too.

[DSM]

Check that all is wired properly. Turn key on(pump runs). Pump should only run for a set amount of time(example 8 seconds). This is also a safety. In case of accident fuel is shut off when engine stops. If this is not working then it may be wired wrong. Also, make sure the tec3r is grounded well. I ran it straight to battery.

[usera]

Well, I am an idiot. The fuel pump relay that I have been diagnosing wasn't even the actual relay. The actual relay was in the engine compartment labeled as bank one relay. I finally dug in (after swapping a bunch of good parts) and made it through the full wiring that was all heat shrink wrapped and saw that the FP relay wire went to a marine grade relay in the back of the engine. $18 later and we are all good.

Thanks for the help everyone.