So I have an 88 Camaro with TPI recently acquired this car and have little info at the moment. I have the inline 20 amp fuse blowing by the battery after start up. Car will crank and fire and run for maybe 3-5 seconds after start up then blow the fuse. Have checked grounds on the heads and such. If I unplug the ecm the resistance goes away on the circuit. If I try to touch the terminals A and B together with paper clip instantly blows the fuse. Most info I have been given is it sat for about 4-5 years and had fuel pump, fuel pump relay, and fuel pump pig tail replaced. Any suggestions? I’m running out of ideas. Thanks

 

The 20 amp fuse powers the fuel pump and ecm. If unplugging the ecm and it doesn’t pop the fuse sounds like the ecm is internally damaged and shorted out.

 

It actually doesn’t blow the fuse until it has fired up and started to run. Then only runs for a few seconds then blows the fuse. I have leaned toward the ecm but wanted to see if anyone had had the similar situation and double check my thought process

 

Koeo it blows the fuse when aldl is jumped ?

 

Yes when I jump it to see if there are any codes it instantly blows the fuse not with engine on just key on

 

I’d probably try a different 1227165 ecm.

 

Thank you so much! I will keep updated how it goes!

 

I'd also be looking hard at the "replaced" wiring.

 

What is the resistance measurement with everything connected? If it is 400Ω or more, that could be completely normal as it would imply a 30mA parasitic draw by the ECM in its normal "asleep" state.

Keep in mind that once the ignition switch is turned on the fuel pump will run a two-second prime cycle, and if the fuel pump or its wiring are shorted or low resistance, that could take the fuse. Also, jumping the ALDL terminals can initiate the fan and fuel pump relays in service mode, which could also take the fuse.

It might be helpful to disconnect the FP relay, install a good fuse, and attempt to jump the ALDL again to help prove the ECM is failed.

Alternately, a jumper wire with a 15A fuse could be used to power the fuel pump directly from the battery to see how long it will run before failing, if it does fail. An ammeter could also be handy for this test, so long as it is rated for the expected current draw (20A or more).

 

I forgot the fan runs aldl jumped, iac also is commanded in at the same time.

 

Ok so I pulled fuel pump relay as suggested and jumped the ALDL again and as soon as key was turned on to get codes it instantly blew the said 20 amp fuse for the ecm/fuel pump which would still imply a shorted ecm internally correct?

 

Possibly. The ECM, its wiring harnesses, or an external load could be damaged. If the ignition is turned on and the ALDL is NOT jumpered to read codes, what happens? How long before the fuse fails, if it does at all? Does the "SES" light do anything?

It is possible that something like this has happened: https://www.thirdgen.org/forums/tech...ml#post6515257

 

ALDL not jumpered and key on fuse will not blow until engine fires to run. Will run for a few seconds then blows. key on engine off won’t blow and check engine light solid on.
I can crank the engine until the battery would die and not blow the fuse as long as it doesn’t start.

also nothing burnt or melted at ecm plugs to suggest overheating or short there.

 

Presumably, when the ECM operates some output dependent on a turning/running engine, something is exceeding design current. If could be internal to the ECM, or it could be external. However, most external ECM loads are ground-side switched, such as the fuel pump relay, EVAP solenoid, EGR solenoid, injectors, etcetera. The few loads that are driven by the ECM are the idle speed control stepper motor (as mentioned by Tuned Performance) and the HEI module bypass. You could try disconnecting the IAC and HEI bypass and sacrifice one more fuse, or try another ECM.