replaced ignition switch
removed viper alarm
3 new relays
new ECM

I tested the green/white wire coming out of the computer and there was nothing coming from that. That is why it a new ECM seemed like a good idea. Still the same issue.

What tells the ECM to send power to the green/white A1?

 

 

Will the pump run at all? Have you tried jumping it to run (regardless of the priming)? Maybe it's the pump.

 

I drive the car every day, the pump seems fine. I just have to crank unitl the oil pressure kicks it on. Could I wire up a switch to prime it before I try starting it?

 

i had the exact same problem. i just ran a line directly to the batter through the firewall and put a discrete switch in. i ran a line off of that under the car and to the pump. just hit the switch a few seconds before you start it and it starts instantly. not to mention its a good way to make a car jacker very frustrated. lol

 

I guess that is the next step for me. Is there existing wiring that could be tapped into or does a seperate wire need to be run? Where did you hook the wire up to the fuel pump?

 

i dunno if this si a stupid question or not, but have u checked the sensor by the oil filter. I forget what its called, but its right next to the oil filter, it has two wires running to it, if its bad it will cause ur fuel pump not to prime, i think.

 

The oil pressure sending unit? I can check, I am open to anything right now. I spend some time on this last night. I went down a check list from BigBabyLou in another post, and the first thing was the fuse by the battery. If I am looking at the right thing, they took that fuse for the amp and put two fusible links off the postive terminal to tie into an orange wire. The checklist says a red and a orange wire attach to this fuse, but I only see the orange. I jumpered the orange and gray at the relay connector and the pump ran. If the oil pressure sending unit sends a signal to the computer to activate the green and white A1 to send power to the relay, I might be in luck. Otherwise I still need to find out what tells the computer to energize A1 and find out why it is not doing it.

 

before you go wiring this up ya gotta try and jump it to see if it is working correctly. but if you run it straight you have to run a wire through the firewall and to the battery. somewhere in this wire install an inline fuse to prevent any damage. take that wire and connect it to a switch under your dash or anywhere close to you. run a second wire off the switch and under the car (following the fuel lines is easiest) and wire it into the sending unit. this is of course if you have an in-tank pump.

i dont think this could be your problem though. this might be overkill because it doesnt seem to be a wire problem if you are able to get the car running still. best to use this as a last resort.

 

I did jumped it using the orange wire to the gray with a paperclip at the relay harness. I might just wire it there.

 

Shribe, don't mess with the oil pressure switch, it's working (otherwise you wouldn't be driving your car every day). It's actually the only thing working in your fuel pump circuit.

The only thing that's broken right now is the ECM's control of the fuel pump via the relay. That's what you need to focus on - how to make the ECM actuate the relay.

Another option, as mentioned, would be to manualy prime the pump by a switch or even better, a momentary button (so that you don't forget it ON). You would have to send 12V to the green/white wire on the fuel pump relay to do that.

Hope this helps a little.
Lou

 

Lou, thanks for hopping in here, your checklist is very helpful. How does the ECM know to actuate the relay?

 

The ECM first turns the relay on for 2 seconds after you turn the ignition on (to prime the fuel system).
Then it starts watching the tachometer signal (from the distributor) and if it sees pulses, it considers the engine running and turns the relay on again.

Since your car RUNS, the ECM must see the tachometer input (otherwise it would not inject fuel, which is timed off the distributor pulses again) so I wouldn't be worried about the input signals.

I'm more worried about your green/white wire from the ECM to the FP relay. In your earlier thread (IIRC) you mentioned that your ECM puts out 12V if the relay is disconnected but if you connect the relay, the voltage on the green/white wire is only 100mV or so. I hope this was your case, I really can't remember with all the electrical problems on the board here, sorry.

There are a few tests to check the green/white circuit that I can think of:
1) disconnect the ECM under the dash and put 12V on the green/white wire - does the fuel pump come on?
2) disconnect the FP relay and measure resistance on the green/white wire against ground and then against 12V (the orange wire for example)
2) reconnect the ECM and stick a 12V light in the FP relay socket - turn the key on - does the light turn on?

Let me know what you find, this is a very peculiar problem.
Lou

 

Step one, putting power to the green/white did prime the pump

Step two, do I measure in ohms, and what setting? I tried it on the tan white wire and got 3.7 and at the green/white and got 2.4 when set at 200 ohms. The other wires I got 1 ?

Step three, checking the green/white at A1 there is nothing when the key is turned.

It goes to another mechanic on Thurday, but I would like to save the $ if I can get it figured out....

 

In step two, did you make sure that both the computer AND the relay were disconnected when measuring the green/white wire? (btw, the tan wire resistance sounds normal). You should have seen 1 on the display, even at the highest ohm setting. If not, then your problem is in the green/white wire - something else might be connected to it. But that's only provided that the measurement was done with the computer AND relay disconnected.

Lou

 

this sounds a lot like what i have happening. i have another post on here and they guys have been telling me to change my 2 year old fuel and see what happens.. which i am doing this weekend! BUT it sure seems like the ecm and fuel pump ain't jivin' together. it primes.. but that's it.

you guys need to get this one figured out so i can see if my problem is the same!

 

I took it to mechanic, who couldn't run it down. He put the prime wire on a switched 12V so it primes and starts. I turn the key and the pump starts and then I crank it and it works. After more than a year, two mechanics, and posting a lot, I need it to start Sorry it won't help anyone.

 

Darn, I was REALLY curious what it was.
Did I mention that I hate unsolved mysteries?

Lou

 

Sounds like a bad connector at the end of the harness going into the ECM.
I would pull the pin out and inspect/replace it.

 

me, too. funny how his won't prime when it's supposed to and mine primes when it's NOT supposed to. still kicking my six o'clock...

 

I AM HAVING THE SAME ISSUES WITH MY 305 TBI , I AM NOT GETTING ANY POWER FROM THE ECM ( GREEN/HITE WIRE TO FUEL PUMP RELAY TO GET IT TO PRIME.....
STILL HAVING ISSUES TO FIGURE THIS OUT CAN YOU HELP