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Engine cranks slowly after warmed up
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Points & Condenser
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Nov 3, 2011, 8:40 PM
Post #1 of 11
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Engine cranks slowly after warmed up
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Hey Guys,
I have been through the mill with this pickup. 1974, Ford F100 302 engine was factory rebuilt 21,000 miles ago (5 years)
I put 4000 miles on this truck a year and sometimes it sits for a month at a time. The gas got stale and varnished the valves in the guides causing several to stick. When I tried to start it a month ago the stuck valves put so much resistance on the camshaft (with Flat Tappet system) that 3 push rods bent in to "S" shapes and the Timing chain jumped a tooth or two. I got a new timing chain and pulled the heads and gave them to an engine re-builder who did a complete valve job on them. He told me to pull the gas tank dump the old gas and wash it out with Lacquer Thinner, flush the entire fuel system all the way to the carb. I did all that and installed a new fuel filter and flushed out the system with new gas. The fuel is crystal clear and has no varnish smell or anything except clean fuel. I reassembled the engine and made absolutely sure every step was done correctly. I paid particular attention to the valve adjustments and the head and manifold torking sequence/psi to specs.The engine started right up and ran pretty good I re-timed the distributor at 6 Degrees before TDC. I am running the Idle at 1000 right now because when I put it in Drive it will stall out unless I give it gas at the same second. I left it running for 2 hours in the driveway and it seemed fine, engine temp 180 oil pressure 50 psi. I shut it off and tried to start it again and it cranked very slow like a almost dead battery, but it was not. It wouldn't start because it was cranking too slow. After 45 minutes I cranks fine again and starts up. I took the advice of a couple of mechanics who said that this was a Ford characteristic and to change to starter and battery cables. I did that today but it is doing the exact same thing. It tries to stall when I put it in gear and it won't start or crank at a normal speed once it is warmed up. I am $500 just in parts and still don't have a truck. I am running out of Ideas here and need advice. Maybe a shout out to old school mechanics, this is an old truck but has an up to date engine.
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Sidom
Veteran
/ Moderator
Nov 3, 2011, 9:40 PM
Post #2 of 11
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Re: Engine cranks slowly after warmed up
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A quick test you can try. Fire it up and let it run til it gets hot & cranks slow. Shut it off, pull the coil wire out of the cap & ground it. Crank the engine, if it cranks at a normal speed the timing is too far advanced...
(This post was edited by Sidom on Nov 3, 2011, 9:40 PM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 4, 2011, 12:16 AM
Post #3 of 11
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Re: Engine cranks slowly after warmed up
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Last year for leaded gas for almost all vehicle. If noticed when heads were off, did pistons have carbon build up? Also, OE real copper wires were good but sometimes under gauge and back then was forever putting on 1 (one) gauge battery cables to starter and ground if battery was known good and plenty of amps. If cables replaced they don't carry full amps like real stranded copper wire. Connections critical also and yes could be a weak starter as Sidom said.
If comfortable and starter brushes suspect as this doesn't have a solenoid on starter you can take it apart and w super fine emery cloth just clean up the contacts of brushes to commutator. Must "clock" motor properly and know how to hold brushes out of the way to reassemble. If it doesn't look good send that one out. Not thrilled with many reman ones,
T
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Points & Condenser
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Nov 4, 2011, 5:37 AM
Post #4 of 11
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Re: Engine cranks slowly after warmed up
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Hey Tom, there was a little carbon buildup on the piston tops, I didn't give it much thought at the time other than most of miles are local driving and I should take it on the highway now and then. I did put a 12 oz bottle of lead additive in the gas as recommended by an auto parts guy who said it was good for the old engines designed for leaded gas. The thing that has me a bit stumped is that before I had this major problem with the engine heads and valves sticking I didn't have any slow cranking problem even with the old cables and starter, it seems related to the repair even though I feel confident that everything was done right. As commented by another reply I will also try the distributor test and see if that is part of it. I'll get back to you, thanks.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 4, 2011, 6:55 AM
Post #6 of 11
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Re: Engine cranks slowly after warmed up
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I've never believed in octane boosters. Real tetra-ethyl lead really did boost octane hence lower grade fuel could be made to behave like like higher grade fuel but did build junk (carbon) up faster.
Current unleaded still can with poke around use especially but slower to do it. It raises compression and more apt to knock and may turn over slower when hot as it's making more compression.
Have timing set where it belongs. Manifold vacuum reading at idle should be close to 18Hg (sea level) a clue that timing is close and compression isn't excessive. Take a couple cylinders and compression test them. Can't hurt. If real high on pre cat/con vehicles there are things you can do with engine intact and running to remove carbon but risk fouling up plugs,
T
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Points & Condenser
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Nov 7, 2011, 8:13 AM
Post #7 of 11
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Re: Engine cranks slowly after warmed up
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Update, I adjusted the timing to start when fully warmed up although it still cranks slower than when it's cold but at least now it will re-start. My other problem still exist when I put the truck in gear it severely tries to stall I am running the idle at 1200 just to prevent the stalling. I was thinking that my tork converter was not allowing any slippage at speeds around 800 as it should. Do you agree? Also is there any way to clean up carbon build up on the piston tops and valves without pulling the heads, (Methods or Products). I wanted to drive this vehicle about 200 miles to move, I was going to tow a small jeep on a tow dolly also with it. I'm debating whether this extra load will tear up the tork converter even more but once the truck is at 30 MPH or higher it runs perfectly.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 7, 2011, 8:37 AM
Post #8 of 11
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Re: Engine cranks slowly after warmed up
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Thanks for following up P&C. This trans should be one of three of the era - FMX, C-4 or C-6 and none used a locking torque converter. Stall RPM would be about +/- 1,500. I don't think that's it.
Didn't re-read whole thread but somewhere in battery power getting to starter in full, good starter, compression and timing are the likely causes. Throw in hidden areas that are too hot too.
Remember that in 1974 "regular" gas was 89 octane not the current 87 or 85 for high altitude or used to do that. Note that engine get hotter by gauge anyway for a while when just shut down and tighter. Timing, idle speed could be adjusted but shouldn't have to go nuts or extremes.
I must have already said, make sure engine cooling is right. Radiator and fan clutch working properly. Let idle a bit before shut down with just raised idle a little which you have done should cool more before shut down if towing or with substantial load. May help to plain flush cooling system and set antifreeze level to say -20F instead of standard 50/50 = -34F which doesn't transfer heat as well. Very strong antifreeze mix will not transfer heat well - know that.
In that changing timing helped try to put what you are at to a #. If premium fuel helps it suggests high compression all defeated as HT mentioned earlier by pulling or grounding out coil wire.
I know it's old now and so am I. Dang - remember cars and trucks older than that in the showrooms NEW. Now many things are on the maybe list,
Tom
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Sidom
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Nov 7, 2011, 12:15 PM
Post #9 of 11
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Re: Engine cranks slowly after warmed up
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Sounds like the timing help a little bit, so that's cool. That test I had you do, with the ign disabled, it should've cranked at normal speed, if it still cranked slow (even if it was faster but still too slow) then there is a problem somewhere else. You didn't post how it did so at this point I'm not sure where to proceed..
There are a lot of things you can do to clean out intake & pistons. A lot of shops offer an induction cleaning, basically a bottle of cleaner hooked up to a vacuum hose & run until the bottle is empty, this does work well.
An old trick was to mist water down the carb while it was running, water is the best carbon buster but you need to be very careful as to not hydro-lock your engine....I'm not sure if they still have them but water injection systems were popular for a while.....
As far as the running problem it's very doubtful it's a converter problem but it would be best to start a new thread for that runnng problem.....If the thread starts to get long, having 2 different problems in one thread gets real confusing....
(This post was edited by Sidom on Nov 7, 2011, 12:18 PM)
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Points & Condenser
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Nov 7, 2011, 5:21 PM
Post #10 of 11
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Re: Engine cranks slowly after warmed up
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Sidom, that bug makes me crazy. If you read what I reply posted to Tom you will have lots of history. I forgot to tell him that I believe the Tranny is a C-6 (the one with the square Pan with a corner out, sort of "L" shaped on one corner) I don't know how old it is, it was on the truck 6 years ago as the tork converter also. I replaced the engine then and left them in. My biggest problem is the stalling when you put it in gear. the slow crank I can live with because it now starts when warmed up.
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Sidom
Veteran
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Nov 7, 2011, 9:13 PM
Post #11 of 11
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Re: Engine cranks slowly after warmed up
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I split your other post into a different topic in this section. We'll use that one for the idle problem.
Before I move on I do need to know how it cranked over with the ign disabled when it was hot.
Did it still crank somewhat slow or did it crank at normal speed???
As soon as I find a better sig...........I'll squash the bug.........
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