Chevy Astro and GMC Safari Forum banner
1 - 12 of 12 Posts

·
Registered
Joined
·
58 Posts
Discussion Starter · #1 ·
Hi, I had my van decide to not start. It turns over but no go. I thought fuel pump,no sound for two seconds, but I don't have power at the pump. Checked relay and fuses and the fuses are good. I don'y have any power on the green and white wire from ECM. I checked continuity on the wire after I pulled the ecm out and wire is fine. I took the ecm apart but don't see anything abnormal from heat on pin or anything. I had also jumped fuel pump and it does build pressure, but wouldn't start and run. This is why I'm thinking ECM. Do they just go bad without any noticable issues. I have notice the last few months while trying to fix EVAC problem that my Reader had a hard time actually communicating with the ECM, but figuired it was the OB II port under dash. Maybe this is connected somehow? Any thoughts?
Thanks
 

·
Registered
Joined
·
35 Posts
I would pull the fuel pump relay and check that positive voltage is making it to the socket for the control side of the relay. ECMs usually have switched grounds, so there may not be voltage there by design.
 

·
Premium Member
Joined
·
17 Posts
What makes you think the pump is the issue? My go to would be crank shaft position sensor. Your reader doesn't indicate this or other code?
 

·
Registered
Joined
·
58 Posts
Discussion Starter · #5 ·
I don’t think it’s the pump. I have no power making it to the pump. I have constant power to the pump relay, but nothing to the green with white wire that comes from the ecm to energize the relay. I know the wire is good from the ecm to the relay by checking it with continuity tester. I get nothing when turning the key on, so I didn’t think it was the crank sensor. My ob2 port has been hit and miss on reading with my computer so I have not been able to check for any codes. Just know I have had an evap code for a year.
is there any way to test the ECM?
 

·
Registered
Joined
·
35 Posts
You should either get 12V or ground on the ECM trigger wire for 2 seconds after keying the ignition on. You could connect a jumper wire to the relay socket to directly connect 12V to the pump. I would try everything to rule out the pump first, it's much more likely to fail than an ECM.
 

·
Registered
Joined
·
58 Posts
Discussion Starter · #7 ·
The pump will run with a jumper wire, so the pump is fine. Do you know if the ecm trigger wire send 12 volts or ground? I checked it for power not ground.
 

·
Registered
Joined
·
35 Posts
Interesting. According to the Haynes manual all model years have the ECM sending 12v to the relay control side of the relay, pin 86. With my (2005) van key off I've got 12v at the relay socket pin 87(inner aft pin), and the other 3 are dead. Key on gives 12v to pin 86(outer aft pin) for 2 seconds, then dead again. Also, 20A fuse ECM-B is the fuel pump fuse. I definitely don't know that because it blew while I was probing with the multimeter.
 

·
Administrator
Common Sense + Critical Thinking
Joined
·
12,417 Posts
So there are two paths to power the fuel pump, see the video half way down the page Fuel Pump Relay and Oil Pressure Sender

If you install a jumper and the pump runs, and is building proper pressure and it's still not starting then it's probably not the pump. Make sure that all of the power and grounds are good for PCM before replacing it.
 

·
Registered
Joined
·
58 Posts
Discussion Starter · #10 ·
I checked grounds and was able to light up a test light by touching just eyelet off wire so I think they are ok. I’m going to see if I have power going to the ecm from ignition switch. I think I found a diagram of the plug of ecm showing the power in on that Same fuel pump plug. Then I’llpull plug wire and see if I have any spark, but it’s been trying fine until now.
thanks for the help
Rob
 

·
Registered
Joined
·
58 Posts
Discussion Starter · #11 ·
I tested the power feed to the same plug that the fuel pump comes from and I do have power to#13 from the switch. I’m leaning in the direction of ECM. I guess I’ll order one and see.
Thanks
 

·
Registered
Joined
·
488 Posts
I tested the power feed to the same plug that the fuel pump comes from and I do have power to#13 from the switch. I’m leaning in the direction of ECM. I guess I’ll order one and see.
Thanks
If you've done anything in the vicinity of the firewal wiring pass through plug, you could have a bad connection in there or a connector that became loose after heating up. Those wires are very sensitive to being moved and sometimes they just get brittle and connections go bad.

I chased similar symptoms for months until a good electrical shop traced it out and found a 2 cent connector in the pass through plug that that become loose and the connector would open up and disconnect when it heated up. Sometimes that was a no start, other times that was a quit running while driving down the road condition.
 
1 - 12 of 12 Posts
Top