OK. What is the new battery voltage with the ignition key on?

George

 

with the new battery going accross the terminals im only getting around .5-.6 /: what should i be testing now?

 

Disregard had a ton of corrosion on the studs, with key on engine off im at 12v at the battery, still only getting.4 volts to the grey wire on the pump. Going from pin 30 to 87 i am getting around 20 ohms of resistance resting and i am getting open when it clicks over. Bad ground?

 

12.0 V at the battery is only 45% charged so that needs to be straightened out or you are going to have a bunch of problems. A fully charged battery is 12.6v.

Where are you testing voltage? At the fuel pump connector, fuse box priming tab, …? Where are you putting the leads? Is this during the initial 2 second prime at key on or after that? Is the fuel pump connected during this test or is the connector off of the pump?


George

 

alright heres what i have done, got the battery to 12.6. At the relay i pulled it up a little but and got my probes under there positive is going to 30 and negative is going to 87. With key on engine off i get OL or open but during the 2 second priming stage i get around 15m ohms so my thought is relay is fine. Last time i checked power at the connector i was at .4 volts. The connector itself is too small for me to get my probs in and test so what i did is i cut and stripped the grey wire and wrapped it around my positive lead and grounded to the bottom of the seat on clean metal. Now looking at the cluster the fuel gauge is correct so at least the reference wire and ground are good. Could the splicer pack in the rear be the culprit?

 

If you have a priming tab next to the relay see what the voltage is at key on for the two second priming cycle and tell me if the fuel pump is connected or not. If not, pull the relay and make sure you have power from the fuse to the relay contact 87 or 30. It’s hot at all times. Positive lead in the relay socket and Negative lead to battery ground. If yes then check the ground side of the relay coil, either 85 or 86 and then check the signal voltage to which ever relay coil contact was not ground between 85 and 86.


George

 

sorry i know im jumping ahead here but really curious what your thought is. I figured out a way to check for power and ground ON the connector. I have low and behold 12 volts of power on the connector to the pump. With the connector off key on engine off obviously i get no power but during the priming cycle i get power! So good news there. Now heres where i would like your expertise. On the ground side with the positive lead on the black wire/pin on the connector and ground lead on frame i get key off i get 7-8 ohms but key on i get 129ohms. Am I measuring something wrong or is there something seriously wrong with ground? For more reference im in the midwest and its pretty rusted.

 

Couple things.

Twice now you have tried to measure resistance on a powered circuit and that wont work. '

Ultimately what matters is that the net voltage to the fuel pump, measured right at the pump is adequate. If the battery voltage is low then of course the positive voltage at the pump connector will be low. If there is excess resistance in the circuit anywhere between the battery and the positive connector then you will have lower voltage at the pump. That same power flows through the fuel pump and then through the ground wire to the frame and then back to the battery negative terminal. Any excess resistance in the ground circuit has the effect of lifting the pump ground from the same voltage drop effect that can happen on the positive side. So lets say corrosion between the relay and pump causes the positive side to drop 4 volts and the ground circuit to lift 3 volts. The pump would only see 5 volts and either not work or burn up. One way to check these circuits is to disconnect them from power and measure resistance between both ends. That can tell you something but may not give the whole picture. The true test is measuring that net voltage under full pump load. Positive and negative meter leads right at the pump connector. If net voltage is low then we find out if its the positive or ground side. You back probe the connector or strip a little insulation off both wires and reseal then when you are done.


George

 

okay sorry for not listening, i redid my measurements and they are as follows. Power side during priming cycle at fuel pump connector: 11.99VDC. Ground side with no power in system going from pump connector to frame: 5.6ohms.

positive test was performed by back probing grey wire with positive lead and large black wire with black lead. Cycled key and observed during priming.

Results:11.99vdc during 2 second period.

ground test was performed with key out of ignition.

Back probed large black wire with positive lead and held black lead to clean frame piece.

Results:5.6ohms

So even though its a brand new fuel pump and the reading are within limits its still not priming. Likely new pump is bad?

 

The pump was connected during the voltage test where you got 11.99V? If yes then did you here anything at key on?


George