250 efi won’t start

[rvaha]

Serial # OT445638. Engine is merc 250 with downdraft intake with Motorola computer. Engine was rebuilt by Chris Carson and has ran perfect for the last couple of year. Last weekend put it in water and no start. Made checks today. Fuel pump appears fine when keyed on - fuel shoots out. Main power relay and fuses ok. Not getting spark with inductive timing light. I’ve separated electrical on engine from boat. I can jumper purple wire to 12v and MPR comes on briefly and turns on fuel pump and briefly puts 12v on ignition coils. I see pulses coming from crank sensor. What am I missing? Did computer just die? Ran perfect before. Many thanks for the help as always. Rick. 540-521-5211

[Savage]

Be careful what you are jumpering power to. PCM provides the ground on some circuits.

[rvaha]

Thanks Savage. Yes I’m aware but thanks for reminder. The book says once the flywheel spins the CPS generates pulses and I believe should turn on MPR and put voltage to both the fuel pump and to the ignition coils. I can force voltage to coils - still no spark. It’s like the kill circuit is engaged but I checked and it’s not grounded. Anything else that might prevent computer from letting it start? If not maybe I have bad CPS or computer. Strange it would die from 1 week to next. Thx again for yours and other faults. Rick.

[rvaha]

Think I’ve found problem. Crank position sensor is supposed to have 300-350 ohms across it. It’s reading meg ohms so it’s open. I think it has to be working correctly to put the computer in run position. So - can I have a drone deliver one today? Rick.

[EuropeanAM]

Good catch. While you're waiting for that- Charge your cranking battery FULLY and test it to make sure it is good. Voltage is critical as that MPR must be able to hold the contacts closed (otherwise no fuel or spark).

[rvaha]

Thanks Don. I have 3 batteries in parallel along with onboard battery charger so should be ok but I’ll double check. Rhonda has one on the way!

[lpugh]

Thanks Don.I have 3 batteries in parallel along with onboard battery charger so should be ok but I’ll double check. Rhonda has one on the way!

That one peaks my curiosity?
Might be a little hard on the alternator if all three get down to a 50% state of charge or less

[EuropeanAM]

THREE cranking batteries in PARALLEL? Your alternator is designed to: "Maintain the Fully-Charged State of ONE Properly Rated, Fully-Charged Cranking Battery".

[rvaha]

Great news. The Crankshaft position sensor I had was bad and the replacement immediately fixed problem. Big thanks to Don for personally taking the package to Fedex - and then they lost it. He went back later while they tried and find it to no avail. I got his last part- so he suggested and provided the number for Sherms marine and then promptly refunded my money. They (Sherms) had it last Thursday and overnighted and it got to me on Friday. About 15 minutes after i got confirmation that the overnight was on the way I get an email from Fedex that the package from don was found and would be there Friday as well. So - from 0 to 2 CPS in one day! And yes, vendor supplies are short everywhere.

Anyway, kudos to Don and Sherms marine for their quick and diligent response!

[EuropeanAM]