View Full Version : PCM start problems

Jeremy P.
07-02-2003, 10:14 AM
" Hello, I have a 350 PCM, holley carb..just had it serviced, it was idling rough and stalled when accelerating to plane. Spark plugs replaced, and accelerator pump arm function fixed. Now the damn thing won't start (cold or hot) easily and occasionally backfires while doing so. Other than the starting problem it runs perfectly now. Which confuses me cause if it runs perfect I should have good ignition and gas flow. I've found that if it doesn't start after 5-6 attempts that if I pull the air filter off and hold the choke plate shut it will fire up (hot engine). Got any ideas? Thanks... "

07-02-2003, 12:12 PM
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08-16-2009, 11:19 AM
"Please help!! I have a 92 supra sport with Ford 351. Never had problems starting, the boat was sitting for about 1-month and when I tried to start it again it will not start. It seems like there is an enormous amount of fuel entering the carb. so i had it rebuilt, i am getting spark at the coil and i pulled one of the plugs and i am getting spark there as well , the coil,distrib. cap and rotor are new as well. I removed the fuel line before the mech. fuel pump to see if maybe the carb. was flooding out and ran it dry, a then tried starting fluid to see if it would fire but still nothing Could. Could someone help,summer is almost over."

08-16-2009, 10:48 PM

should have started a new thread.

first guess - get your manual out and recheck the firing order - each wire and at both ends. Fords and Chevy's use a different numbering pattern so verify what you did is correct with that manual.

second guess - you mentioned a lot of fuel into the carb and it was rebuilt but not whether the 'flooding' still exists. if so, check the clear tubing at the fuel pump. If its wet, the pump is leaking and needs to be replaced. failure too do this will continue to flood the carb. Also, pull the dipstick and smell the oil. If its smells like gas, change it and the filter, too. Diluted oil will cause bearing failure."

08-17-2009, 08:51 AM
"Yes the flooding still exists with the rebuilt carb. The firing order is correct. But why if I drained the carb. and tried starting fluid would it not fire, if I have spark."

08-17-2009, 01:36 PM
Either no compression or spark occurs at the wrong time...sure the distributor went in correctly?

08-17-2009, 01:51 PM
did not install new distributor. How could it have no compression when it ran perfect for 2-yrs. Something to do with sitting for a month. Never had a problem with timing and did not adjust or touch distributor.

08-17-2009, 03:14 PM
misread - missed the "cap".

It may have compression - that's leaves the fuel and the spark....Have you put a timing light on it to verify the distributor cap and wires function as required?

Checked for fuel in that tube?

08-17-2009, 03:26 PM
I would bet on no spark. A bad wiring harness or a bad ballast resistor could be the problem. A timming light should indicate if there is spark as stated by Makomark.

If you check the distributer besure to use the firing order for a Ford HO engine.
HO is 1-3-7-2-6-5-4-8

08-17-2009, 03:36 PM
"I pulled two of the plugs and grounded to motor mount and I do have spark, could it be the plugs are fouled and if so would they show a spark?"

08-17-2009, 03:38 PM
As far as the firing order goes I numbered each plug wire before I removed the old cap and replaced each in same as was when the boat was running fine

08-17-2009, 04:36 PM
"Usually, a fouled plug won't spark. You can always replace them. On occasion, i've seen plugs show spark when held to the block but misfire in the cylinder.

Robert's observation of the ballast resistor being bad has caused more than one owner to sell his boat."

09-22-2009, 09:13 AM
I need a wiring Diagram for a PCM Marine Engine 454 long block. 1982 Supra Sport Ski Boat. Any help would be appreciated

Travis Burril
07-14-2014, 09:20 PM
If the engine doesn't start hot then its vapor locking and u need to cool the filter or check the pump