Merc 5.7L Keeps Dying

[Bondo]

Re: Merc 5.7L Keeps Dying

Bondo, I think merc had allot of blocks in storage when GM stoped making the mech fuel pump boss. I have a K serial # 5.7L that has mechanical pump. According to merc, it was made Sept '96.

Thanks John,....... Sorry Johnson....

 

[Silly Seville]

Re: Merc 5.7L Keeps Dying

Bondo, I think merc had allot of blocks in storage when GM stoped making the mech fuel pump boss. I have a K serial # 5.7L that has mechanical pump. According to merc, it was made Sept '96.

I've been wondering about that because I have a '96 Vortec 350 sitting here that has the mechanical pump provision too.

 

[sjohnson44]

Re: Merc 5.7L Keeps Dying

Thanks John,....... Sorry Johnson....

Alls well man.

Ive found that I'm losing spark when the engine dies. Hooked a timing light to the high tension lead and hooked a multimeter to the positive terminal on coil. Cranked engine and immediately timing light started flashing and motor ran, also 14V at coil.
Motor ran for about 20 secs, and then the light quit and motor died, still had voltage at coil. Tried to recrank the engine, engine would turn over but timing light would not flash. Waited about 15secs, and tried again, timing light flashed and motor cranked right up.

Im going to try to go through that no spark flow chart when I get the no spark condition and see what I can find.

 

[Don S]

Re: Merc 5.7L Keeps Dying

Disconnect the gray lead on your tachometer (Not on the coil) and try it. The way the TB5 ignition is set up, you can't just remove it from the coil.

 

[dubs283]

Re: Merc 5.7L Keeps Dying

my wag is ignition sensor in the dist

i have found that is usually the culprit in a t-bolt no spark situation

anything but the latest style, fully potted oem sensor - replace it with the new one

 

[sjohnson44]

Re: Merc 5.7L Keeps Dying

I have the tach disconnected already, I disconnected it last night while checking for spark to see if I could get a change.
I had thought that maybe that would be the issue because my tach did not work, but still has the same problem.

 

[Don S]

Re: Merc 5.7L Keeps Dying

Hook up a volt meter between the negative terminal and a good ground. Start the engine and see if the voltage stops at the same time the engine does.

 

[sjohnson44]

Re: Merc 5.7L Keeps Dying

I checked voltage a negative side of coil and the voltage seemed very inconsistent. Jumping around from 12V to 15V but the engine was also running rough. After it finally died, I still had voltage and tried a restart and would not fire. After waiting a bit, tried to crank and it fired off and ran a lot smoother. Voltage then was stable at 15V on (-) post on coil.

After the engine died I started with the TB5 flow chart and got down to the wht/red connector and had 11.4V coming from the module. I rechecked all connections at battery and breaker and rechecked all grounds and managed to get 11.8V coming from module. Not sure if I should have stopped there or not, I continued to the next and disconnected the high tension lead from distributor and hooked my spark gap tester to a ground and unplugged the wht/grn connector and struck the lead coming from the module against ground repeatedly and did not get a spark from coil.

This suggests my ICM is to blame. I have done this test multiple times and still get the same result. I have checked all connections at the plug to the ICM all are good, and have checked all grounds.

Number on the ICM is 807264-3 57L Alpha

 

[Don S]

Re: Merc 5.7L Keeps Dying

Did you re-connect the red/white before doing the green/white wire test for spark?

 

[sjohnson44]

Re: Merc 5.7L Keeps Dying

Yes I did.

 

[Don S]

Re: Merc 5.7L Keeps Dying

Might want to re-read the chart again before the sensor.

 

[sjohnson44]

Re: Merc 5.7L Keeps Dying

Installed new Mercury coil for my engine, now motor will not run at all.
The coil fires when trying to crank and the motor will hit, however when you let the key go it doesnt try to continue running.

After messing with it some, I did finally get a no spark condition while cranking. I ran through the flow chart again, and I still was not getting spark when tapping the wht/grn wire.

Im going to replace the key switch and the sensor before I buy the module. Will replace both tommorrow and check back with results.

 

[Don S]

Re: Merc 5.7L Keeps Dying

Hook up a jumper from the battery positive terminal to the + terminal on the coil and see if it starts. That eliminates everything from the ignition switch to the coil (Including the ignition switch).

 

[sjohnson44]

Re: Merc 5.7L Keeps Dying

Got new sensor installed and got motor to run again. Still dies. Hooked jumper from batt to coil and still dies.

 

[sjohnson44]

Re: Merc 5.7L Keeps Dying

807264A01 - ICM CONVERSION KT (#807264A01)

Is this the number I need to order for the module? I dont understand why it says Conversion kit, I just need a module.

 

[sjohnson44]

Re: Merc 5.7L Keeps Dying

Any ideas guys? Have I gone as far I can go and need an ICM now?

I keep hearing how these things never go out, but I have read about people having them go bad. Plus its the only thing that aint new.

 

[KD4UPL]

Re: Merc 5.7L Keeps Dying

I have a '97 Mercruiser 5.7. It was always hard to start. I always had to crank it and crank it. It seemed like it didn't have spark but eventually it would start. It never died on me. I had the ICM replaced. It starts great now every time. They do go bad.

 

[John_S]

Re: Merc 5.7L Keeps Dying

807264A01 - ICM CONVERSION KT (#807264A01)

Is this the number I need to order for the module? I dont understand why it says Conversion kit, I just need a module.

The new module is larger and uses different connectors. The kit includes splicing the new connectors in. I changed mine a couple of years ago. Not hard.

 

[sjohnson44]

Re: Merc 5.7L Keeps Dying

I hope they go bad. I hope mine is fubar'd. Cause I got one yesterday next day air'd to me. So this is will either be an epic fail, or hopefully an epic win.

 

[John_S]

Re: Merc 5.7L Keeps Dying

I hope they go bad. I hope mine is fubar'd. Cause I got one yesterday next day air'd to me. So this is will either be an epic fail, or hopefully an epic win.

Rather pricy, aren't they? I was about to offer sending you my old one, for diagnoisis, but saw this. Mine had completly different symptoms (little to no advance). Ran at idle fine.