pulled fuel line off before filter fuel pump gives very small squirt of gas and shuts off is second
new fuel pump

 

Well, I guess that's another way of doing it

I hope you had a hose going into some type of container, if the pump had worked, you would have had a very large gasoline spill under your truck.

 

poked hose in to a gas can any idea why pump wont stay running is it posable to hot wire pump to switch

 

The pump is suppose to only run a few seconds when you turn the key to on (not cranking the truck just to make the dash lights all come on and seat belt buzzer if you haven't removed that yet) it only continues to run when you go to crank it over and the engine is running.

 

Ditto ^^

Without the engine running, the pump goes through it's couple of second ON cycle and then it shuts off. To restart this cycle, you need to turn the key off and back on, then you get another couple of seconds of ON. If you're cranking it, I believe it should remain ON and then stay ON when the engine starts. I've never had the pump running with the line disconnected, I usually connect the pressure gauge and check things out from a standing position - much safer and cleaner that way.

It's the ECU that gives the pump that couple of second cycle - that's not built into the pump. An electric pump can be hot-wired, and then it would run continuously as long as the power was applied (or until the pump failed). I wouldn't advise hot-wiring anything that's near (or immersed in) gasoline. I've done quick tests on pumps before, but I've always removed the pump to do this - don't run the pump dry for long. Generally, if the pump runs for the couple of seconds with the key in the ON position, it'll run continuously. If you get no flow, the pump could have failed (normally they just won't run when this happens) or the screen at the bottom of the pump is plugged (you need to take the pump out to see this).

 

as i said before new pump,screen,and filter so no clog.so im tring to understand pump receives a second singnle to continue running,could this b a ecu issue? because when it does start seems not change chugs and stalls

 

I believe this has been explained several times, but just in case it wasn't clear, I'll lay it out one more time in point form, here it is:

• When a vehicle has been standing (not running) for a while (a few hours, overnight, etc.), the fuel pressure usually drops somewhat.
• When you turn the key to the ON position, the ECU allows the pump to run for 1 or 2 seconds to build up the pre-start pressure. This is done so that if you do want to start the car, you have pressure and if you just want the key ON without starting the car, the pump isn't running continuously.
• If you want to re-run the 1 to 2 second pump cycle, you need to turn the key to OFF and then back to ON, and each time you go from OFF to ON, you'll get this short run.
• When the car starts, the pump is turned on to run full time.

If you want to test the pump outside of this environment, I'd advise you to pull it and hook it directly to a 12 volt supply and see what it's doing.



Since you've changed the screen and unhooked the fuel line before the filter, you should be able to see fuel coming from the line during this 1 to 2 second cycle. You can try turning the key between OFF and ON 3 or 4 times and if you don't get a really substantial fuel flow, I'd say you have a bad pump.


With all this explanation, I'm assuming that your pump does run for a second or two when you turn the key to ON and also, that the pump runs continuously, when you start it. What I'm saying here is that you need the fuel pump relay to stay on as well as the pump being able to pump for everything to work. Again, not to beat a dead horse, if you had a pressure gauge, you'd see either very little pressure when you tried to start it (this would lead me to believe the pump was bad with everything else that you've tried) or you'd see the pressure jump up and then die down as the engine stopped (this would lead me to believe the relay might be bad). Many of the relays in your power distribution panel are the same, so if you swap the fuel pump relay with one that you don't need to start or keep the engine running, you should be able to test the functionality of that - personally, I'd prefer to use a multi-meter for this test.



I don't know how to explain it any better than what I've just done - it's a simple system with very few rules, and I don't know what other guesses to give you if you won't do any tests.

 

Okay, maybe I didn't read this closely enough - it would be easier to understand if you didn't put a whole string of things into one sentence.

I just noticed that you're saying that this is the second NEW fuel pump. I think you need to check the power in your fuel system to make sure you have good connectivity to the fuel pump relay, past the relay to the fuel pump connector. I would also want to make sure that I had a really good ground for this circuit. If you aren't comfortable using a multi-meter, I'd suggest finding someone that knows how to do this - a corroded connection or broken ground can put enough resistance in the circuit to make the pump motor work very poorly.

I'm hesitant giving you advise on playing around with live wires around the fuel pump when you have that fuel line disconnected, so what I will recommend is this:

• Since you've already had the pump out, take it out again.
• You'll see a connector with 3 wires - one is for ground, another is for the fuel level sender signal, and the third is for the pump power.
• Usually the black is ground on a vehicle, but I'd suggest you get a wiring diagram of your vintage Dak and look at that circuit to make sure.
• Next, I'd find which of the other 2 is pump power. If you just hook up a car battery to the ground and the wrong wire, you can fry the sender.
• Once you find the pump power, you can actually see if the pump runs & if it does, I would be looking for the bad connection or ground in your current hookup. I don't know how much you know about continuity testing, so I can't give you any recommendation on doing this right now.

 

pump had a bad contact,fixed but still wont run. pressure on fuel rail on key hits 40 psi but drops to 31 psi and holds. during cranking is 39 psi steady

 

Well at this point it doesn't sound like a fuel delivery issue.have you checked out all of your sensors?
After replacing my fuel pump my truck still had issues starting. I replaced the crank position sensor and cleaned the Iacocca valve and now it runs like a top. A faulty map sensor can effect it too. Make sure they're all getting power. have you pulled your injectors to see if they need to be cleaned?