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View Full Version : Electrical/technical- Help Jim?


PE4ME
05-12-2005, 01:33 AM
Pulled a major Dumas this weekend and between my step-dad and I, we managed to hook up the battery backwards in my PS 205- 350 TBI. 30 seconds with < 10volts of charge. Cant imagine the shear anger and colorful language display.
Anyway, here is where I am at:
gauges work, fuel pump cycles,(this indicates some function of ECM) pumps and motor turns over.
No spark...juice to coil, juice from coil to ignition module(IM); however no juice from coil to dist. cap... supposedly the IM processes juice from coil, communicates w/ECM to ultimately control ignition firing- IM-ECM-coil-distributor...solid state wiring set-up???
I am hoping IM took the toll and saved ECM???
no breakers tripped- :2 of the 3 fuses off ECM have juice to fuse, one has no power- this is powered up when engine is running??? (lost hear) did not follow dead fuse back. This is all when key is "on"
Please no name calling- what an idiot...confused:
:confused:
thanks for the help...

PE4ME
05-12-2005, 01:37 AM
Fair price? part #?
Will any GM TBI module work? This is INDMAR but will one off a mercrusier work? Looking online at diagrams, they look the same but are the programed timing curves compatable and did they share same/compatable ECM?

jimmer2880
05-12-2005, 07:14 AM
really wish I could help you. Unfortunately, all I can do is hand you a virtual beer & say "yup - that really su(ks dude". We've all done pretty stupid stuff before - don't sweat it.

Hopefully JimN or EngineNut will respond soon.

JimN
05-12-2005, 08:27 AM
By TBI module, if you mean the ECM, Mercruiser used the Delphi unit for a while, but changed to Motorola around 1998. If you got one, it would need to have the same output for fuel pump relay(+ vs -) and would need to be programmed for your boat. You need to check voltages on any wires that are applicable. It's definitely possible that your ECM is a goner. They don't like being connected with reverse polarity and I'm not aware that they have any internal protection for this.

Check your main circuit breaker.

Engine Nut
05-12-2005, 08:36 AM
Pulled a major Dumas this weekend and between my step-dad and I, we managed to hook up the battery backwards in my PS 205- 350 TBI. 30 seconds with < 10volts of charge. Cant imagine the shear anger and colorful language display.
Anyway, here is where I am at:
gauges work, fuel pump cycles,(this indicates some function of ECM) pumps and motor turns over.
No spark...juice to coil, juice from coil to ignition module(IM); however no juice from coil to dist. cap... supposedly the IM processes juice from coil, communicates w/ECM to ultimately control ignition firing- IM-ECM-coil-distributor...solid state wiring set-up???
I am hoping IM took the toll and saved ECM???
no breakers tripped- :2 of the 3 fuses off ECM have juice to fuse, one has no power- this is powered up when engine is running??? (lost hear) did not follow dead fuse back. This is all when key is "on"
Please no name calling- what an idiot...confused:
:confused:
thanks for the help...

You can be pretty sure that the ignition module in the distributor has been destroyed. (Indmar P/N S556096) That is generally the first thing to go. The ECM does have some reverse current protection. I suspect it may be OK. If the ECM was bad, a MerCruiser ECM wouldn't work without being recalibrated and then only if the GM part numbers on the back of the old and new ECM were the same. We sometimes see the diodes in the alternatot take a hit from reversed polarity. I would start with the ignition module. New ECM's are in the $1000.00 price range

Engine Nut

PE4ME
05-12-2005, 09:28 AM
Huge- thanks
circuit breaker- wouldnt this kill everything? (big one in rear of motor, red button)
it turns over and fuel pump runs...everything responds...no spark.
diodes did do some welding, melted a post, there was a loose connection so it was arcing on post otherwise i would have never known battery was in backwards...
Also, radio turns on does all the functions but no sound to speakers. by by amp? is the fuse protecting the amp only- cant believe it would power up but not send sound...

Anyway- thanks for your wisdom.

Diesel
05-12-2005, 10:52 AM
I did this once in an 87 model Chevy pickup I just finished swaping long blocks. It took out the ECM, dist. module, and the alternator. I actually cranked the sucker for a while before I noticed, so I might have done more damage with the cranking :eek: . The circuit breaker will only trip if the circuit is shorted. It has no way of knowing if the polarity is reversed (same for fuse). You might be able to find someone that can rebuild your ECM for a little less money. You will still probably have to get the programing redone.

Good luck you might be chasing bugs for a while. :)

PE4ME
05-12-2005, 12:38 PM
yeah- sucks, the only good thing is i restored this from the ground up so i know where everything is...however the electrical gremlin is one of the most difficult to shake...

anyone know of a used site/business?
mercrusier part looks identical but??? timing-circuitry is different? seems odd, looks like indmars version is 175 and merc is 85...again look identical.

bunji69
07-16-2008, 09:52 PM
I have the exact same symptoms you had with your boat in 2005. No spark to Dist. Cap, but everything else checks out. Did you ever figure out the problem?? Please Help!!!!

kevinfavors at gmail dot com