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Tech501
Tech501, Auto Service Technician
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Experience:  38 years exp, ASE Mastertech with L1 Advanced Engine performance
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1990 Chevy: Van..Spark..The ECM1 Fuse was blown

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I have a 1990 Chevy G-20 Conversion Van. It has no Spark. The ECM1 Fuse was blown. It has the 305 engine, TBI, and a 700r Trans. I have replaced the Distributor, Cap, Rotor, Ignition Module, Starter, Battery, Coil, and checked all connections recently. It was running fine, I parked it and it hasn't run sense. I suspect the ECM, but can not find the thing to replace it. Where did they hide it on this van? I have pulled the dash and can not find it. Manual says it is under the drivers side seat, it isn't. Thanks for any [email protected]
Try inside passenger compartment under the right hand side of unstrument panel.
Customer: replied 11 years ago.
Reply to DCM's Post: As I said, I have pulled the dash, including the instrument panel and have not found the ECM. My past experience has been that they are usual under the dash on the passenger side, but I have not found it there or on the drivers side. Also, besides the ECM, would anything wlse I have no replaced cause a No Spark issue?
Have you look by the engine compartment?


On your 1990 CHEVROLET TRUCK G20 3/4 TON VAN, the ENGINE CONTROL COMPUTER is:



FRONT SEATING AREA, DRIVER SIDE, UNDER SEAT, ABOVE    
TRACKING RAILS, MOUNTED IN CENTER OF SEAT RISER
SUPPORTS


 


This is where it is supposed to be although, I wouldn't rush to replace it. The fact that the fuse of blowing can be an indication of a problem with one of the components that is operates like a fuel injecter or solonoid. As you can see in this schematic, it operates a few components. I would highly suspect either a fuel injecter or the EVR solonoid but some testing must be done.









 

 


 


Copyright © 2002 Delmar, All Rights Reserved.




Customer: replied 11 years ago.
Reply to Tech501's Post: OK as I said, this is a conversion van. It has Captain's Seats. I know the manual for the van says it should be under the seat, I have the manual. It is not there. It is also not under the dash anywhere, either near the engine compartment or anywhere else. I have completely removed the dash to make sure it was not hidden. I have removed the engine cover to make sure it was not in the engine compartment, it isn't.

So, to make absolutely clear:

This is a 1990 Chevy G-20 conversion van. Manufactured 5/23/1990 by the Glaval Mfg. Corp. It is chasis type 90CV2 production number is XXXXX

It has the 305 engine and the 700r trans. It has TBI. I located a brake control module in the driver's side fender so I assume it has ABS of some sort.

I have located several electronic components that where attached to the emergency brake bracket. I found them looking for the ECM several weeks ago, but have been unable to identify what they are. Non of them match the part numbers I have for ECM modules, but maybe someone will know what they are:

Component 1:
Delco Electronics Corporation 06 MAR 1990
AGI 25110385
36AGI X079188

Component 2:
AC 05/04/90 9:25AM 009
25110868
37FA

Component 3:
Letron Rochester ML
15599007
0121


Any clue what they are? Anyone have a manual specific to the Glaval Conversion?
 OK, your truck has been mdified since keaving the factory. When it left the original factory, the ECM was under the seat. The company that did the conversion has relocated it somewhere. There is no way for us to know where. There will be a large bundle of wires leading to it from the engine compartment so you should be able to follow them to whereever they put it now. Remember what I said, your likely chasing to wrong thing here anyway. The problem is most likely in one of the components powered by that fuse and NOT the ECM itself.
Customer: replied 11 years ago.
Ok, well,

When I had checked the fuses the ECM1 fuse was blown. I replaced it and have tried to start the van several times since. It has not blown again.

What, other than the ECM would cause the van not to spark?

Again all grounds have been checked, it has a new distributor, coil, control module, cap, rotor, battery, starter, etc.

 Actually the ECM will not prevent ignition. You need to also check for injecter pulse with a noid light (shown below). The first step is to check for power on the positive side of the coil and one sid of the injecter plug. If you have the power supply and yet no pulse on either one, your not getting reference signal from the distributor pick up. If it turns out to be only ignition with no pulse, use your noid light across the coil + and - of the plug and crank to check for pulse. If you do have pulse, the coil is bad. If you do not have pulse, your looking at a problem with the ignition module or power supply to it on the pink wire coming from the ignition switch. Get a better picture of what you do or don't have and we can narrow it down.  


 


Customer: replied 11 years ago.
Reply to Tech501's Post: I have been told that the ECM is located under the window panel in the side of the van on the driver's side of the vehicle on the conversion vans.

The Coil and Distributor(including pickup coil) are brand new in the van. What else could be the issue? Would the electronic spark control, voltage regulator or some other part not yet replace prevend firing?

Again the Complete distributor, coil, plugs, wires, ignition module, starter, and battery are new. All grounds have been checked, cleaned, and reconnected.
I guess your ignoring my previous answer.
Customer: replied 11 years ago.
Reply to Tech501's Post: No, I simply do not have a Noid light and can not find one at the parts store. I am of the opinion the guys at the store have no clue what it is. But they do not have any out with the tools.

Can not do the test with out the tool.
I just bought 2 of them in AutoZone for $6.99 ea. this morning. Your right, the guy at the counter asked me what they were.
Customer: replied 11 years ago.
Reply to Tech501's Post: Thats what I thought. So how do I explain what it is to them so they can find it? Also, is there any chance the ECM will have codes stored that will be accurate, or is that barking up the wrong tree, yet again?

Just show them the picture. It will be in the tools isle.


There may be codes in there. It's worth checking. Here's the procedure.



To extract a trouble from the computer for diagnostic purposes, the Assembly Line Communication Link (ALDL) connector is used.


Ground terminals A and B with the ignition "ON" and engine not running. The system will enter the diagnostic mode. In this mode, the computer will display a 12, three consecutive times, by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" or light. A 12 consists of one flash, a short pause, then two flashes in rapid succession.


After 12 is displayed, any stored trouble s will be displayed by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" light. All s are displayed 3 times each then a 12 will repeat. In the diagnostic mode, the computer will also energize all computer controlled relays and solenoids.




ALDL Connector (Located Underdash)

The ALDL diagnostic connector is located in the passenger compartment.


Tech501, Auto Service Technician
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Customer: replied 11 years ago.
Reply to Tech501's Post: I have located the ECm in this vehicle. It is in the kickplate located by the step on the drivers side.

This is a bad loaction as any water from your shoes and weather will eventual work its way into the ECM.

The housing of my ECM is coroded and the PC Board has obviously been shorting out for some time. There are some very bad scorch marks on the PCB.

I believe the ECM will have to be replaced before looking for any other problems. HArd to say what components have been blown by the short.

Tech 501 you have been very informative and I am releasing the funds to you. I will get back to you as soon as the ECM is replaced and I have run all the diagnostics I can.

Thanks for the help.

Customer: replied 11 years ago.
ECM has been replaced and the vehicle is now running again.
Glad to hear that.

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