Engine no start after ECM put back in

[Jetjock]

I was having some issues with my engine after getting a code 31. After doing the diagnostic, it indicated the ECM as the culprit. It started and run ok before I took it out. I sent to it to Haibeck and had it overhauled. According to what he told me, after it was done, it worked great! He put it in a ZR-1 and it worked flawlessly. When he shipped it back to me, I was tied up with work and moving. Finally, got the chance to install it and I started the engine or so I thought. Engine turned over no light off. One thing that I noticed was the lack of fuel pump noise when I tried to start the engine. I replaced the fuel pumps about a year and a half ago because the sending unit broke. Tomorrow, I'm goin to hook up my fuel gauge and check to see if that is actually the problem. Is there any other thing that I can check into? I do have the manuals for the car. I appreciate any help that you guys can do.

Roy

[TX '90 ZR1]

Roy,
I would feel confident that if Haibeck worked on it and said it was good, it was good.
I'd check all the connectors to the ECM first to make sure they are mated properly.
After that, you're down to air, fire and fuel.
I would think Haibeck will be glad to visit and help you get it figured out.

[32valvZ]

Are you certain the prom is fully and properly seated?

[Jetjock]

There was a note on the ECM that stated that it was.

Roy

[Jetjock]

Originally Posted by TX '90 ZR1

Roy,
I would feel confident that if Haibeck worked on it and said it was good, it was good.
I'd check all the connectors to the ECM first to make sure they are mated properly.
After that, you're down to air, fire and fuel.
I would think Haibeck will be glad to visit and help you get it figured out.

Haibeck told me that he ran the ECM in a car at his shop so I feel pretty confident that its not the ECM. These fuel pumps are relatively new and came out of 94 Z that the guy replaced with something else. The car is in a garage so it's not exposed to the elements. I'm doing a check of the fuel pumps then move on. The thing that blows my mind is that it started up every time. so something has happened in the last month or so to cause this to happen. We will get through.

Roy

[Paul Workman]

On the 90s, the (edit) MDS* sensor is under the ECM bracket. (edit) 93+ the MDS is under the plenum.

With the ignition switch OFF, current applied to the fuel pump test connection* is between 4-5 Amperes for each (8-10A total)

*Fuel pump test connector is a connector on the end of about an inch or so, jutting out of the big wire loom, near the windshield wiper motor.

I think most would agree that having a scanner that will read OBD-1 codes is worth its weight in GOLD when it comes to trouble shooting. (Mine has saved me countless hours of trouble over the years! Just sayin!

*Manifold Differential Pressure sensor (thank you Jerry for clarification)

[kapkanimd]

Originally Posted by Paul Workman

With the ignition switch OFF, current applied to the fuel pump test connection* is between 4-5 Amperes for each (8-10A total)
[/I]

Can you clarify what you are saying here? What is it you are testing with the pump jumper?

[Corvette95]

Originally Posted by 32valvZ

Are you certain the prom is fully and properly seated?

This is where I would start first... its a 60 second check. There are two 7 or 8 mm screws on the ECM with a metal plate. Remove the cover and make sure the PROM is properly seated. Disconnect battery first. Also, highly unlikely but assuming no hard part issue with your car (blown fuse/Vats/etc.) the PROM could have gotten zapped by an x-ray scanner during transit. When you turn the ignition on (ignition on NOT running or trying to crank) is the check engine light on in the DIC? Is you SYS indicator on in the cluster etc?

[Paul Workman]

Originally Posted by kapkanimd

Can you clarify what you are saying here? What is it you are testing with the pump jumper?

To test the current draw of the fuel pumps, the quick check to see if the current draw is normal is to set your VOM (volt-ohm-meter) to read AMPERES:

1st!: Before making any connections to anything, switch the (usually RED lead) to the "A" (Amps) port of the meter. (AND! Remember to disconnect the leads from the meter BEFORE you return it to read voltage or ohms. Otherwise you will likely blow the meter's internal fuse if later you accidentally attempt to read voltage while plugged into the amperes port!)

2nd: WITH THE IGNITION SWITCH IN THE OFF POSITION, jumper the (black) lead of the meter to the the fuel pump diagnostic connector - the black (or sometimes white) connector attached to the short read wire (jutting out of the wire loom between the windshield wiper and the brake booster. (Use an alligator jumper to make this easier -- see photo))

3rd: Touch the other meter lead (red) to the POSITIVE battery terminal and read the current on the meter. Barring a bad fuel pump(s) or blown fuses, each pump should draw 4-5 amperes for a combined total of 8-10 amps. If one of the fuel pumps is inoperative, a reading of 4-5 amps indicates one pump is not operating. Check the fuses before assuming fuel pump(s).

WHEN FINISHED, DISCONNECT THE LEADS FROM THE CAR AND REMOVE THE RED JUMPER FROM THE METER'S AMPERES PORT AND PLACE IT ON THE OHMS/VOLTAGE PORT ON THE METER BEFORE READING VOLTAGE.

Note: If the pumps are drawing the typical amount of current (4-5 for each), chances are the pumps are operating OK. Otherwise, each pump has a fuse to consider. And, if fuel pressure (which I suggest you also monitor while conducting this test) is not in the 43-45 ish PSI (ore better) range, there may be a delivery issue (e.g., bad check valve or kink in the line, etc., etc.)

[Jetjock]

Originally Posted by Corvette95

This is where I would start first... its a 60 second check. There are two 7 or 8 mm screws on the ECM with a metal plate. Remove the cover and make sure the PROM is properly seated. Disconnect battery first. Also, highly unlikely but assuming no hard part issue with your car (blown fuse/Vats/etc.) the PROM could have gotten zapped by an x-ray scanner during transit. When you turn the ignition on (ignition on NOT running or trying to crank) is the check engine light on in the DIC? Is you SYS indicator on in the cluster etc?

What kind of damage could an x-ray do to an ECM? I do have SYS light and the check engine light on.


Roy