Hard starting when hot (flooding or starter issue?)

[johnunit]

I've got a strange issue.

When starting from hot (10+minutes of running time) the car cranks over very slowly. It will generally not start unless I put the pedal to the floor. It seems to be the action of having the throttle open that helps it start, not the squirt from the accelerator pump. I can put the pedal to the floor, leave it for a few seconds, and crank the engine over and it will start/crank almost normally and fire quickly. This happens even if I only turn the car off for a few seconds and then turn it back on, or if I leave the car for 20 minutes after getting it nice and warm. It basically sounds like I have a half-dead battery. I can keep cranking pretty much forever (until I'm worried about hurting the starter) and the cranking won't slow or speed up, but flooring the gas pedal will start it.

The two thoughts I've come up with are:
1. my starter and negative battery cable are both aging (are these standard parts store parts?) so they may be getting hot, weakening the flow to the starter somewhat

2. my (possibly unrebuilt) variable venturi carb is flooding. this would also explain the sense I get sometimes that I've lost a bit of gas while the car is parked, though this may just be the tempermental gas gauge fooling me.

I don't have issues with it "loading up" and in general it seems to be running well, no misfires etc. Pumping the acc. pump at idle makes the engine stumble or even die, which I know on Holleys at least is a sign of a relatively rich mixture.

Any thoughts?

[Brandon]

Sounds like a starter and a carb problem. I know my carb does the similar thing. Except I've learned it from not holding it to the floor but barely and I mean barely mashing the gas as I turn it over and it'll fire right up. Those carbs have their own weird little ways about them.

[gadget73]

If the engine is turning over slow, it may be a weak battery or a weak starter. Sometimes the starters will heat soak from being near the exhaust and get weak when hot. I know cars with long tube headers are well known for this.

[marquisman]

yeah, id check you battery and/or starter. also check you cables. did you rebuild the carb or was it sent out? the float might might not be set right.

[1990LTD]

heatsoaking the starter. how old is it?

[sly]

the choke could also be choking it some and putting the pedal on the floor will force it open IIRC.

[marquisman]

yea, forgot about the choke. the choke on the VV is a joke anyway. when the old mer had the VV in it, the choke was disconnected and set fully open. never had an issue

[johnunit]

how do I check the chokes on these? I gather they aren't the traditional type where you can just look for the choke to physically open.

I doubt it's the battery, as it's fairly new and has never show any signs of weakness other than this. I have an exhaust leak somewhere on the right side, possibly forward of the cats, so starter heat soak would make some sense.

I'll check if hitting the gas before (but not during) hot crankover fixes the issue, since that'd point to a choke problem.

I have no idea when the carb was rebuilt, if ever. It could have been done the day before I got it, could be untouched 1985 gasketry in there.


Either way the negative battery cable and the starter cable look original, so that'll be replaced soon, hopefully that fixes the issue. I guess I could also find a junkyard car or something to steal some of that metallic heat-reflecting junk and wrap it around the starter to see if that makes a difference.

Thanks for the advice people.

[351m]

I have to agree with fixing the starter, the carb is a totally separate problem but honestly, if the starter isn't working right you won't know.

[watchdog]

I had the same problem in the 1991 P72. Before you change any parts look at the ground cable on the negitive side of the battery.(not the battery cable itself but the ground cable that goes from the -termnal to the fender)

The small yellow cable in this pic.

Mine was too small and corroaded (sp?) and would drag the starter every time it got hot. I didn't even think about this until I saw the insulation melting when my roommate tried to start the car one day. Replaceing this cable solved all my starting problems.

Also, I have swaped out the carb on mine with an edlebrock 600 cfm 4bbl and I still had the same problem, so it's not the carb.

[johnunit]

That sorta supports what I observed with the hot (literally) wires. I'm going to go through when I have some free time and just replace every wire going to the battery.

[johnunit]

After giving this a lot of thought (and being rained out from installing my new battery and starter cables), two things occur to me:

1. despite having a theoretically identical engine bay, I've NEVER had that third "ground" wire Watchdog is talking about. I've also not had the problem with starting until a few months ago. I'm not sure if that means I don't need that wire and it's unrelated to the issue in my case, or it means not having it has worn other junk out causing the problem

2. I've bumped my timing ahead in very small increments over the last few months, could advanced timing cause the issue? It only has issues HOT starting, but I've still heard of advanced timing making the car harder to turn over.

[marquisman]

what did you bump your timing to? too much advance could have somethin to do with it. best thing is to set the timming to spec, then see what happens