5.0 EFI blowing 10 amp fuse

[Banshee595]

Hi, I have a 2000 mercruiser 5.0 EFI blowing 10 amp fuse. I have found same problem with search but with no solutions.
Symptoms were, no spark, no injector pulse, no fuel pump and no starting procedure beep.
Figured that if i unplugged fuel pump the 10 amp fuse wouldn't pop and I got spark. So rigged up test lead to fuel pump to battery +, cranked engine and manually ran pump. Engine started no problem. I turned it off and tried again. This time no spark and no injector pulse but fuse has not blown.
Any pointers on this one? I have searched and come up with exact same problem on same engine but no solution. Anyone come accross this one before? Thanks

 

[alldodge]

What is the motor serial number?

 

[achris]

We also need to know if the ECU is a MEFI1 or a MEFI3.

Chris...........

 

[alldodge]

Did a bit of looking based on an assumption of what you have, still need serial to verify.

Fuses
10 amp ECM/Injector/Ignition/Knock Module
15 amp Fuel pump
15 amp ECM/DLC/Battery

Could be one of your injectors is drawing to much current, or knock module or the ECM

 

[Bt Doctur]

15 - Fuse (15 Amp) Fuel Pump 16 - Fuse (15 Amp) ECM/DLC/Battery 17 - Fuse (10 Amp) ECM/Injector/Ignition/Knock what fuse is blowing, you have 3

 

[Banshee595]

Hi, thanks for replies.
it's MEFI 3 and I'll get ser number in the morning.
It's the 10 amp fuse that's popping. Or was I should say. It's not blowing now and still no spark or injector.
Knock sensor unplugged and no change,
fuel pump being unplugged allowed spark. Albeit for a brief moment. Engine ran for 3 seconds and I turned of. Cranked again and no spark or injectors again.

 

[alldodge]

To disconnect the knock module it would be the connector attached to the distributor. unplugging the sensor wouldn't change things.

Since its not blowing the fuse again I'm starting to lean toward ECM. Could disconnect one of the injectors then try the other one. This way if something is pulling to much and it starts might have another clue

 

[Banshee595]

Thanks, wasn't sure about the knock sensor, although only wires into distributor are the pink and pur/wht onto the two white wires.
the fact it's not blowing the fuse again is concerning.

 

[alldodge]

Excuse me, I misspoke, the MEFI 3 has the knock module inside the MEFI, its not external.

Look for the tachometer to show around 300 rpm when cranking. If your getting the rpm then need to check the distributor. If your not getting the rpm then may be the ECM

With a pink and purple/white you must have the EST distributor

If ECM needs to be tested/repaired. If so I would recommend
https://obd2allinone.com/ecmrepair.asp

 

[Banshee595]

Thanks alldodge, will check as you suggest tomorrow and hopefully it's not the ECM, although I suspect it might be..
Thanks for your help..

 

[Banshee595]

Did the ignition module test and no spark. Replaced coil with known good one, retest and no spark. So looked like ECM, bought an ignition module for the hell of it and engine fired straight up.
thanks for the help..

 

[alldodge]

Thanks for the update and it does get costly

Did you get one from Bob at obd or another place?