So, I have a 1983 for f250 with a 351W that's been giving me some trouble for the past about a year. Every time you start it , if you drive for a bit to get it warmed up, then shut it down, it will not start back up. It will crank but very slowly, almost like the battery is dead. But the thing is, if you let it sit for 5-15 minutes, it will fire right up. And this doesn't seem to happen when the engine isn't fully warm so I can drive it for about 2 minutes and shut it off then start it up just fine, but drive for 10 minutes then try it again, it won't start. I've replaced the solenoid on the inner fender at least 3 time. I have also replaced the starter back in august 2015 and put a heat wrap thing around the starter to try and keep heat from the headers off it but that didn't work. I am completely stumped and have no idea what is wrong. Anybody have any insight or suggestions?

 

I had this same issue with a 1986 f250 with a 351w. What caused my problem was a bad battery to block ground.

When i discovered that was the fix i replaced my battery to solenoid wire and my solenoid to starter wire

 

Run a voltage drop test on the supply and ground sides of the starter circuit. This test confirms the strength of the battery under load and the ability of the cables, solenoid, and all connections to deliver those pesky electrons without undue restriction.

I swear by this test for diagnosing any circuit with subpar performance, such as a slow starter. It will easily find faults that won't show up with an ohmmeter. It's very simple and easy to do. It will take you longer to read these links than actually running the test:

Voltage Drop Testing

Diagnosing Voltage Drops - Electrical Automotive Troubleshooting

 

My vote is the timing is a little too far advanced. What do you have it set at?

 

I would not even go thru all the trouble of measuring the voltage drop on EACH batt. cable just replace them.


If timing was never changed then that would not be the cause of the motor slow to crank when hot.
Now as you heat up cables the resistance goes up, less volts to everything and the motor will crank slower.
AND PLEASE do say they look good. Once you have them replaced cut open the old cables and tell me what you find!
Dave ----

 

Um, Dave, have you ever actually tried a voltage drop test? The beauty of the test is you don't have to disconnect a blessed thing and it tests ALL parts of the circuit at once. If you do find a fault, you can then zero in on the specific area, but the initial test looks at the whole circuit first.

I've had many instances where friends have called me AFTER replacing batteries, starters, and solenoids, sometimes more than once, thinking the new parts were bad from stock. Two minutes under the hood with a meter and I could conclusively point to a marginal crimp at a cable end, or whatever the fault was, and not the starter, etc.

Once you understand how this test works and how amazingly simple and accurate it is, get yourself fitted for a cape because people will think you're a superhero when it comes to electrical troubleshooting.

On the other hand with this situation, the problem could very well be a timing issue as you've suggested. I'd still suggest running the voltage drop test first to rule out any electrical supply issues to the starter. Then you could proceed with confidence, knowing the problem lies elsewhere.

 

KR, no I have not only because most of what I deal with who knows how old the cables are.


Some of what I work on for fun (my cars) is pushing close to 50 years old and again I don't know how old the cables are before I got the cars or truck. So 1 of the first things in rebuilding is to replace the batt cables and I have never had any issues with starting hot or cold.


I have also cut open the old cables that looked good on the out side but where all green on the inside. This is why I said don't look at them as you can't tell if good or not.


I also have been told that the cables can measure ok but when you put them under the high amps like when starting when hot is when they fail. How can you test the cables under high amps to see if you have a voltage drop?
I say just replace the 30+ year old cables and be done with it.
Dave ---

 

Dave, come join me on the dark side! Resistance is futile. Two minutes with a voltmeter is all I ask...

As far as your question of how can one test the cables under the extra load of cranking a hot engine, how about warming up the engine and running the same exact voltage drop test? I should have specified that in the first place. I was thinking that and it's not my fault if you can't read my mind.

Something else to consider if just replacing the cables without testing first. Many aftermarket cables have marginally sized conductors, hidden under fat insulation so they look good. The brand you use might be fine, but our poor original poster might inadvertently pick up cables made at the Fling Dung factory in China. Let's say his original cables were bad, and we've both arrived at the same conclusion, although we got there differently. Meanwhile, even with no other faults, the new substandard cables can't handle the massive amp draw needed to crank a hot engine. The cables must be good because they're new, right? What's next? Battery? Starter? Solenoid? Repeat the voltage drop test and it will show the new cables as the problem.

Respectfully submitted.

 

If you want to see if the timing is hurting you, when it gives you trouble get out and pull the connector off the ignition coil. Then crank it over. If it spins really fast then, you know the timing is giving you a problem. If any wiring has been done under the hood it could also be a problem with the timing start/retard feature not working on the durspark II module.

When I see the mention of "headers" I suspect a engine that is non-stock where lots of things have been messed with including the timing and the wiring.

 

Great idea on disabling the ignition. I'll have to put that in my bag of tricks.

Glad you mentioned the headers. It reminded me about the wraparound heat shield on the starter. Although one would deflect some heat, I've always wondered if it would also act like a blanket and still trap whatever heat did get inside the starter. It seems a flat insulated baffle would be better than a wraparound shield.

 

I had a chevy where the advance weights would get rusty and stick once in awhile. A trick that worked with it till I could pull the cap and use some wd40 was to pump the pedal a couple of times before cranking. This would flood the engine and it would crank over faster. This trick would let it build a little momentum cranking, and when the plugs would clear up you could hear the engine start slowing again but it would usually crank right up.

 

I'm pretty sure the engine has been rebuilt at some point, mostly because I found a user that used to have the truck and they posted something back in 09 wondering if they should buy it, and they mentioned that the ad said the engine was rebuilt. As for the wiring, it is a horrible mess of redneck butchery. Also, it's not giving any symptoms of bad timing, when cold starting, it runs flawlessly with no backfiring or any type of rough running.

 

The timing can be a little too advanced and it will really run good, but give you a slow cranking problem when hot. That is why the factory put the spark retard feature in the ignition box. But you can still advance it so far that even that doesn't work. Or you can mess with the wiring and the retard feature will not work at all.