Fuel Pump Priming?

[30 PSI SHADOW]

First thing in the morning,or if it sits long enough,If i turn the key to accessory,should the pump prime the system and give some sort of fuel pressure?Mine doesnt, and it only gives pressure till i turn the starter over.Then it takes a second for it to start.If i shut it off for a few minutes,its fine,as it holds pressure(anti-drainbacks fine).
Should it prime the system on accessory??

bill

[turbovanman²]

Whats the fuel pressure like overnight, does it drop?

Check for power when turning over, could be a sign of a bad ASD relay or the pump/reg might be on its way out. As soon as you turn on the key, the pump is turned on for a few seconds then off, then on again when you crank it.

[30 PSI SHADOW]

) pressure overnight....

[Turbodave]

It won't prime when you turn the key back to the "acc" position, but it should prime when you turn the key forward to the "on" position.

[sdac guy]

No, the pump should not prime when the key is switched to accessory. The fuel pump, coil, and injectors are all fed off of the same 12v from the ASD relay. The ASD should never be energized when turning the key to the accessory position. As Simon said, only when turned to On or Start.


Barry

[gvare001]

Under what circumstances could the fuel pump be getting power without the ASD relay on?

[30 PSI SHADOW]

The ASD should never be energized when turning the key to the accessory position. As Simon said, only when turned to On or Start.


Barry


OK, then it should prime the system for a quick second when switched to on,right? I only get a working pump when i hit the starter.

bill

[30 PSI SHADOW]

any idea why?

[sdac guy]

Under what circumstances could the fuel pump be getting power without the ASD relay on? It is not supposed to. The ASD relay is actually a safety device. It is supposed to kill the fuel pump, coil, and injectors if the engine should stop turning (in the case of an accident turning off those items minimizes the chance for a fuel related fire).

If your fuel pump is getting power when the key is off, or when the engine is not turning with the key on (other than when first priming) then there is probably a wiring error or short somewhere.

Barry

[sdac guy]

OK, then it should prime the system for a quick second when switched to on,right? I only get a working pump when i hit the starter.

bill

Are you sure? Don't rely on listening to it, new pumps with a full tank can be very quiet. To check for certain, carefully release the pressure in the fuel rail at the schrader valve (use a rag to soak up the escaping gas while doing this). Then put a fuel pressure gauge on the rail and turn the key on. Watch to see if the pressure rises on the gauge.

The ASD is supposed to energize for about a half second or so when the key is first turned to the on position. I have seen corrosion on logic module connectors keep this from happening, but it also kept it from coming on during cranking.

Barry

[turbovanman²]

The best way to check is put a test light on the coil + terminal and place it so you can see it. Then turn the key on, should be off, then another click and you should get power for 5 secs or so then go out, then crank and of course, it should be solid. If no power when switched on, you need to start tracing wiring diagrams as could be a bad ignition switch, possible relay, computer etc.

[30 PSI SHADOW]

The ASD is supposed to energize for about a half second or so when the key is first turned to the on position.
Barry

I have a fuel pressure gauge inside the car. When you first turn to "on", Nothing... only when i actually hit the starter do i get ANY fuel pressure.Might be a ignition switch..

Must be deeper in the wiring...guess i need to start tracing it back.Just thought it might be something easy.
I wonder if this is causing my detination problem over 10psi. Nothing shows a lean condition,And the scanner shows my timing is bouncing around under boost.strangest ghost ive ever seen.Ive been dealing with this for a loooong time.

thanks bill

[sdac guy]

The ASD is supposed to energize for about a half second or so when the key is first turned to the on position.
Barry

I have a fuel pressure gauge inside the car. When you first turn to "on", Nothing... only when i actually hit the starter do i get ANY fuel pressure.Might be a ignition switch..

Must be deeper in the wiring...guess i need to start tracing it back.Just thought it might be something easy.
I wonder if this is causing my detination problem over 10psi. Nothing shows a lean condition,And the scanner shows my timing is bouncing around under boost.strangest ghost ive ever seen.Ive been dealing with this for a loooong time.

thanks bill Try a different ecu or lm/pm. If it was the ign sw, then it wouldn't work when running, as after starting it returns to the on position.

I agree with Simon's advice though, put a test light or meter on the coil + terminal and see when you get power there.

Barry

[devlish]

I'm having a similar problem with my 85GLH. the pump does not turn on at all. we just put in a known good pump, and still nothing. there is power, albeit weak, at the plug for the fuel pump. i'm thinking ASD relay, any other ideas? going to check for spark tonight, forgot to do that last night

[lametec]

If the pressure leaks down to nothing, the 2 second prime sequence isn't enough to build pressure. Try turning the key back to off, then back to on again. It should prime again. It'll only do this 2 or 3 times before it stops priming all together for a while.

How long does it take for the fuel pressure to get back to 0? If within seconds, you have a bad check valve in the fuel pump.

[turbovanman²]

If the pressure leaks down to nothing, the 2 second prime sequence isn't enough to build pressure. Try turning the key back to off, then back to on again. It should prime again. It'll only do this 2 or 3 times before it stops priming all together for a while.

How long does it take for the fuel pressure to get back to 0? If within seconds, you have a bad check valve in the fuel pump.


Or a badly leaking injector or bad fpr, ;)