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I have a 86 6.9l F250 4x4. The thing starts fine cold but hard when its worm. I mesured the amp draw of the starter and got the following results: On a cold start the truck pops on so quick its hard to get a good reading but the numbers I saw were between 370-650 amps. Starting when worm is another story my meter will bouce between 500-800 amps usualy above 600a and it may take from 5-10 seconds of cranking to start. Is my starter begging to be replace (any recomendations on brand or oversized)? or could this be a timing isue. The glow plug circut seems fine and the plugs are new (clicks on and off happly with a 150a draw when on). Injectors are new, ip may be questionable. Comptession is 250-350. Batteries seem fine as the turck will start just the same after sitting almost 2 weeks.
The starter is most likely going bad, possibly in the solenoid. Delco Remy are fairly reliable starters. The OEM sized starter should be sufficient as a replacement.
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If it starts good cold that usually indicates the motor is strong, low compression or a worn motor will be very difficult to start when cold and start better when hot. As for your starter its hard to say, the most critical test for the starter is the speed it will crank the engine. Most tech manuals for diesels require a cranking speed of at least 200 RPM. I'm not sure what the amp draw should be on a 6.9 but 800 amps sounds high. If you could borrow a photo tach and check cranking speed you may find your problem good luck.
You said the IP was questionable......... you only get a few chances at diagnosing an IP. If the engine starts fine when cold and hard when hot a worn out IP is suspected. To diagnose it, you pour cool water on the rear of the IP when it will not start hot...the cool water shrinks worn areas in the IP and it should start like it did cold.
Thanks for your input. I suspect that both my sarter (should not pull over 400amps) and IP (empty the truck is a dog off the line and barely can get it slef up hills) bad. I will be replacing my IP end of next week and I will update then and turn to the starter after that.
CONCLUSION:
i got my rebuilt injection pump and one injector and that helped the starting maybe a little (runs MUCH better now though). replace one battery and that helped a bit more. Went to AST on Jerrold on San Francisco and got the recommended Mitsubishi starter with stepdown gears and now the truck pops on!