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Thanks to everyone's help, I've rebuilt the front suspension and got the charging system fixed and now I'm moving onto the starting issue. The truck in question is a 1981 F150 2wd w 302 5.0L V8. I can start the truck when its been sitting no problem, no need to pump the gas, nothing just a nice clean start. When I have driven the truck (usually only a few miles to a store) and get back into the vehicle to start it, I have to pump the gas a few times to get it going. Then I'll drive a few miles and stop, do my thing and try to start it again and it takes quite a few times of pumping the gas and turning it over to get it start and smells very much like gas. Now if I do this start stop start stop 3 or 4 times over I eventually get to the point where I cannot start the vehicle no matter how much I pump. I usually let it sit for an hour and so and then when I get in its pretty easy to start. So a few things to note here, the temp gauge always spikes to the max after a minute or so of operation and this was noted by the PO but he did the whole "Feel inside the engine bay it's normal temp" - I'm inclined to agree but not sure. When I get to the point where she wont start, I pull the air filter off and manually pull the throttle on carb and there is always a good amount of vapor coming out when the choke plate opens. I haven't tackled the vacuum lines yet, but I will say that there are quite a few lines capped - maybe this plays into it. I did tune the carb which was extremely rich to baseline (newish carb, previous owner bought a reman and had it sitting in the truck for prob 4 years? with intermittent use). Perhaps a carb rebuild is in order. When the carb was super rich the truck had really bad bogging down issues from gear to gear and since I've baselined it, it is still there but not anywhere near how bad it was before. I by no means have it where I want it to be, but there were other issues that needed to be addressed first. So you guys always give me great starting points and I appreciate it, hopefully I can get this bad boy out of the way and start tinkering with the mig.
I wouldn't gamble with the engine temperature if I were you. Either fix the gauge or get an aftermarket, numbered gauge. They are pretty easy to install.
If the engine really is overheating, it sounds like your thermostat may not be opening, and therefore you don't have any or enough coolant flowing through the block to cool things down.
The starting problem sounds like a rich or flooding condition compounded by the high temps vaporizing gas out of the float bowls.
First things first, take care of your engine and make sure it's not overheating. Overheating will kill any of the engines in these trucks, even if they may be reliable in other ways.
Check the choke make sure it is off when the engine is hot.
And best to get an after market temp gauge so you know what the engine is actually is.
If it running hot you may be getting vapour lock. Regardless you need to know if the engine is running hot or not.
the temp gauge always spikes to the max after a minute or so of operation
Only when the engine is already at normal operating temperature? Or does it do this from a cold start, too?
Factory gauge? Lots of people diss on the factory set-up, but I have found mine to be very reliable. Just be aware the factory gauges are deliberately slow, to hide minor oscillations. Expect maybe a ten second delay for the gauges to respond, which is no big deal. Most gauges are like that, so don’t be alarmed.
I wonder if your temperature sender may be on its last legs, and is sending an inaccurate high signal when only slightly above normal. It’s perfectly normal for the coolant temperature to climb a little after shutdown, but typically we don’t see it because we’ve already turned off the ignition, and thus the power to the gauges.
Try this for some cheap and easy troubleshooting. Warm up the engine as normal. Shut it off, and then switch on the ignition again, but without starting the engine. I think the accessory position will even power the gauges, IIRC. Watch what the gauge does for ten or twenty minutes. Remember, it’s normal for the temperature to rise a little. But if you see it spike high, that would likely indicate a bad temperature sensor acting up.
I think you may have 2 things going on here and could both be a cause of the hard start warm / hot.
there is always a good amount of vapor coming out when the choke plate opens.
Originally Posted by matthewq4b
Check the choke make sure it is off when the engine is hot.
And best to get an after market temp gauge so you know what the engine is actually is.
If it running hot you may be getting vapour lock. Regardless you need to know if the engine is running hot or not.
Your quote and Matt's is the choke opening all the way when the motor is up to temp?
This is the first thing to check and adjust the choke as needed to make sure it is open all the way when hot.
Originally Posted by kr98664
Only when the engine is already at normal operating temperature? Or does it do this from a cold start, too?
Factory gauge? Lots of people diss on the factory set-up, but I have found mine to be very reliable. Just be aware the factory gauges are deliberately slow, to hide minor oscillations. Expect maybe a ten second delay for the gauges to respond, which is no big deal. Most gauges are like that, so don’t be alarmed.
I wonder if your temperature sender may be on its last legs, and is sending an inaccurate high signal when only slightly above normal. It’s perfectly normal for the coolant temperature to climb a little after shutdown, but typically we don’t see it because we’ve already turned off the ignition, and thus the power to the gauges.
Try this for some cheap and easy troubleshooting. Warm up the engine as normal. Shut it off, and then switch on the ignition again, but without starting the engine. I think the accessory position will even power the gauges, IIRC. Watch what the gauge does for ten or twenty minutes. Remember, it’s normal for the temperature to rise a little. But if you see it spike high, that would likely indicate a bad temperature sensor acting up.
Yes the temp gauge will climb a little, don't think it should "spike" when you come back to start it.
This is because of what is called heat soak. Motor is off but the metal is still hot and coolant is not flowing so the coolant picks up the heat from the metal. When you start the motor and hot coolant starts moving and hits the temp probe it shows a higher temp.
It should not spike. Because it is cheap I would replace the temp sender and if still not fixed or just do it, add an after market gauge so you know what is going on.
With knowing what is going on with the temp we can see if that is causing the hard start.
But there are a few things to check and do.
First check to make sure the choke is open all the way when motor is warm / hot like at the first stop. If not you need to adjust the choke so it is open all the way.
If the choke is open all the way climb up and look into the carb and see if fuel is leaking into the carb.
Now move the throttle you should see fuel squirt. If not we will have to do more digging why. Is it because fuel boiled out of the bowl (the fuel leak above) or bad pump?
Each carbed motor has it's own knack to start both cold & hot, thing is it takes time to fine what yours needs.
Don't pump the gas when trying to start when out. If you smell gas it could be from the pumping and flooding it.
When warm and if all is good you should not need to hit the gas just turn the key and it should start. Maybe press it down a little (1/4 way) and hold it there then try and start is all it should need.
Worst case hold pedal to floor till it starts but should not need to do that or pump.
Another test involves ice, a drag racers trick of sorts. Get a bag ice cubes, pull the air filter and plug any vacuum lines. Now go for your ride to the store when you stop put the bag of ice on top of the carb, try not to cover the black choke housing, close the hood and do your thing.
When you come out pull the ice off carb, note if choke is closed (hope not), close the hood, 1/4 down on pedal and start the motor. If it starts sooner than any time before carb could be heating up.
Dave ----
When I get to the point where she wont start, I pull the air filter off and manually pull the throttle on carb and there is always a good amount of vapor coming out when the choke plate opens.
"when the choke plate opens". That is suspicious right there. Like a couple others have said, check the choke. On a warm day, after you have driven it a few miles and then it sits, the choke should be almost to fully open. You should not see the choke plate closed.
Go out and open the hood, take the airlcleaner off, and look for a large round black thing on the carb. This is your choke adjustment. See if it has rivets holding the round black piece on, or does it have screws. If it has rivets, they will need to be drilled out and screws put in their place. If you have to do this, you might as well get a rebuild kit, they usually have the screws included.
If you already have screws, take the truck out for a drive, let it sit, where you know it will give trouble starting. Instead of starting it, go out lift the hood, take the aircleaner off, and look at the choke. If it's shut or almost shut, that is a problem. Loosen those screws on the black round piece, and while holding the throttle halfway open(engine off) turn the black piece till the choke opens up. Let go of the throttle and tighten the black piece down. Then go in and see how it starts. If this fixes it, then you may have other problems on a cold morning start up, but we can address those if it comes up.
Okay so update, yesterday it was about the coolest day we’ll have here in the summer heat and I fired up the truck. The temp gauge slowly rose (when it is much hotter outside it rises quite a bit quicker) and it took maybe 10 min at isle to reach the upper threshold of the C H gauge and lingered there until I began driving, then a mile or so in it went past the line in the threshold towards the H. So I’m thinking the temp sender is working but I am going to replace that and the thermostat just to be safe. I did mess with the fast idle and now I have no hesitation between gears, yay! But I do believe the engine is running hot. One other thing I saw was the carb vent bowl solenoid had exposed corroded wires. From reading about this, it’s more for engine off heat soak conditions regarding fuel vapors, worth swapping out while I’m at it?
On the carb vent solenoid, just pull the large hose off the carb and leave it open. See if that helps hot starting. If it does, then yes, you could consider replacing the vent bowl solenoid if you can find one.
Dave, I'm not sure where I picked up on the "pump the gas pedal repeatedly" to hot start. Pushing the pedal down (more in the 1/2 way range) works very well. It starts very easily then. I replaced the temp sender and thermostat last night, tonight I'll refill my fluids and see where I'm at. The bottom right screw on the thermostat housing was the toughest bolt I've dealt with on the truck. The manual casually states remove both bolts but you have so little clearance you almost have to remove the distributer. Alternating between a 1/2" and 13mm wrench I was able to tighten it back up after about 30 min lol. I guess someone had the same clearance issue as me before so that bolt had barely any torque on it, I'm surprised it didn't leak. I can't remember for certain but I'm thinking when I pulled out the tstat, it was in the wrong direction.
Also, what about the fan clutch? The manual states "With the engine cold (not run for at least one hour) and stopped, rotate fan by hand and feel motion. The fan should have some viscous drag and move smoothly through a full rotation. If the fan is not smooth, has no resistance, or does not turn at all, replace the fan clutch." I can't rotate mine without considerable force, and even with that, it doesn't spin it just moves as far as I can push it. I'll have to double check that mine is equipped with a fan clutch since it states (vehicles so equipped).
If you have a very large aluminum looking thing in the center of the fan blades, you have a clutch. If the clutch is locked up, you can usually hear it when the engine revs, it's pretty loud. If it's not locking at all, it may run a little warm on a hot day in town traffic.
The carb does have a "clear flooded engine" mode, and if the choke happens to be closed, if you floor the gas pedal, there is a linkage that will force the choke door open some so the engine can get air. The choke system is fairly complex on these engines, a lot of little things to go wrong over the years which add up to a large mess to figure out. Many people just convert to a manual choke. Doing that it will work much like a older lawnmower or weedeater. You choke it when it's cold, and then manually turn it off when the engine warms up. And it will be much like the weedeater or lawnmower, you will have to learn how much choke the engine wants and when it wants it to keep it from stalling.
It turned out to be a shotty cut-to-fit bypass hose. I didn’t notice it until I put coolant in today to test it and the temp gauge rose again (I’m thinking the temp gauge was bad too, didn’t ever want to go down once truck was off until I pulled key out and put it back in) and when I was installing the bypass hose I noticed that at the 90 degree bend, the hose was almost closed from a too long cut hose(the pic doesn’t do it justice, on the truck it was more constricted). Anyways I got a new hose and aftermarket temp gauge. I fired it up and the temp rose to 195(rating of my tstat) and then dipped back down to 180ish. Then slowly rose to 195 and stayed there. A few mile trip of stopping and turning it back on and it fired up no problems and stayed at 195 the whole time. I’m thinking since the passage to the tstat was so constricted there was no possible way the tstat could open. I don’t know when the p.o. had the work done so I have no idea how much damage has been done to the engine aside from the 250 miles I’ve put on since I bought the truck.
the hose was almost closed from a too long cut hose(the pic doesn’t do it justice, on the truck it was more constricted). Anyways I got a new hose and aftermarket temp gauge.
A few mile trip of stopping and turning it back on and it fired up no problems and stayed at 195 the whole time. I’m thinking since the passage to the tstat was so constricted there was no possible way the tstat could open.
Great find. That little bypass hose has always puzzled/irritated me. I never understood why the cooling system was designed that way. Seems such an important passage could have been cast into the block or water pump, but what do I know? Nobody asked me...
Just curious, did the stock gauge behave itself once you got the coolant flow sorted out? In other words, it may have been reading correctly all this time and the coolant temperature really was spiking high shortly after start-up, just like the factory gauge showed.
Great find. That little bypass hose has always puzzled/irritated me. I never understood why the cooling system was designed that way. Seems such an important passage could have been cast into the block or water pump, but what do I know? Nobody asked me...
Just curious, did the stock gauge behave itself once you got the coolant flow sorted out? In other words, it may have been reading correctly all this time and the coolant temperature really was spiking high shortly after start-up, just like the factory gauge showed.
I haven’t tested it yet, but will prior to installing routing the new gauge through the firewall. I’m pretty curious myself, just didn’t want to fool with it again today. I’ll report back once I test it.
07-06-2018, 03:31 PM
