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He evreryone hope all is well. It's been a long time since I posted but I have done ALOT. since my last post I have replaced the :radiator, water pump, thermostat, fuel lines,fuel pump, wheel studs, u joints, transmission extension seal, wheel bearings and brake hoses. It's been quite the journey so far but she runs and drives now. The lil Lil red express is having some problems though. Mostly heat. Like overheating and vapor lock causing no start and the battery drains out from cranking. My fix idea. Electric fuel pump right after the tank going to the mechanical pump so whenever you need to refill the vapor locked lines you can flick the pump on. Can you run electric with mechanical. And how would I run a return line on the stock thermoquad? My other idea is I have two tanks and to hook the electric pump up to the second tank before the switch over solenoid. So normal operation you run in the primary tank. And during starting you flip to the secondary tank and flick the fuel pump on to "prime" the system. How does this sound. Or is it better to get rid of the mechanical pump entirely and just run electric and a return line somehow. Thanks guys and btw how do I solve this cooling debacle. I have a 180 thermo in there rn and it holds cool on the freeway in 100 degrees but as soon as you slow down below 40 or it gets over 100 degrees it immediately climbs and keeps climbing until it pegs to H and pukes coolant!
 

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I would try to diagnose and repair the overheating issue first. Is the radiator fan coupling clutch OK? Coolant flow OK?
Then follow up with fuel system modifications, if necessary.
What is the current fuel pressure from the mechanical pump you have now?
Any higher-pressure electric fuel pump would require rubber hoses that can withstand the higher-pressures and a fuel pressure regulator at the carb float inlet. If the fuel is boiling in the float bowl, the higher-pressure leading up to the carb won't help you. Pressurized fuel can be passed through the mechanical pump within design limits. You don't want a mechanical pump diaphragm rupture or fuel leaks of any kind, anywhere.
Any pinging, spark knock or detonation under load when warm? Leaner mixtures will burn hotter.
 

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Thanks for the reply! The fab clutch is good, coolant is new and full and I dodid two complete radiator flushes to try and get the junk out there was alot. When I checked last the mechanical pump was pushing 7/8 lbs of pressure. Which from my knowledge is perfect. The electric pump is purley so when the fuel evaporates I can quickly fill the system again with liquid gas without having to crank it over until the battery dies.
 

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I'm with IC: fix the overheating instead of trying to jury-rig a fix to the vapor lock problem it's causing. It sounds like you have an air and/or coolant flow problem. Given that you have already replaced th water pump, radiator, and thermostat, and have good cooling at higher speeds, I suspect air flow.
 

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Idk why I didn't think of that lol it's kinda obvious. I even told everyone it can handle 50+ mph because air is getting shoved through yet somehow I dkdidnnake the connection for lower speeds. I also thuth a big part of it is 105+ friggin degrees in stop and go traffic with a 360 v8 and A/C running. I tell my dad not to but I can't blame it when it's that hot .but what's really weird is depending on the day eveiif it's 105 out it'll be ok but sometimes even on the freeway it overheat miserably. Like Wednesday we were going home it was like 103 out and it held cool the whole way to our destination but on the way back going like 65 it just started to climb and kept climbing even after I slowed to 50. I feel like I should also mention this thing has 4 somethings for the final drive ratio so it's probably doing a good 3,200-3,500 rpm the freeway a lot more rpms than I like.
 

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You replaced the radiator and say there was a lot of 'junk' in it? From what?
A flush can push out the softer debris and deposits, but if there is hard scale and/or lime deposits, then that must have come from somewhere else like the block?
Most any older cooling system will struggle at over 100°F, but something sounds wrong. It shouldn't peg or puke.
 

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Discussion Starter #7
I replaced the first radiator because it was punctured and plugged up with dirt. While the pump and radiator was out I pulled all of this big chunks of rust out of the hose and block entry, an there was a lot of brown and white crap with the texture of like clay in there as well. Did as much as I good could but some still probably got in the new radiator. The entire cooling system when we got the truck was rusted to heck and I spent an hour pulling rust of the block and hoses. Now I know 100 degrees is hard but what kills me is it'll hold at just above C on the freeway on like 90-100 but it fools you because in stop and go traffic the temp gauge shows it at cold and then all of the sudden it just starts moving up really fast without warning. And nothing helps after that: heater does nothing, ac off does nothing, constant airflow just barely holds the gauge in the upper 3/4 of it's travel. But like I said this is completely based on the day. Sometimes it'll fire up and drive and never overheat other times it'll overheat in 5 minutes. Drives me nuts.
 

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I replaced the first radiator because it was punctured and plugged up with dirt. While the pump and radiator was out I pulled all of this big chunks of rust out of the hose and block entry, an there was a lot of brown and white crap with the texture of like clay in there as well. Did as much as I good could but some still probably got in the new radiator. The entire cooling system when we got the truck was rusted to heck and I spent an hour pulling rust of the block and hoses. Now I know 100 degrees is hard but what kills me is it'll hold at just above C on the freeway on like 90-100 but it fools you because in stop and go traffic the temp gauge shows it at cold and then all of the sudden it just starts moving up really fast without warning. And nothing helps after that: heater does nothing, ac off does nothing, constant airflow just barely holds the gauge in the upper 3/4 of it's travel. But like I said this is completely based on the day. Sometimes it'll fire up and drive and never overheat other times it'll overheat in 5 minutes. Drives me nuts.
Ok here's one question. Does it have a fan shroud? And second is the radiator the right size? If you're running in that kind of heat, and A/C running that radiator better be the biggest one that would've fit that truck.
 

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Intermittent overheating can happen. You want to jump in and diagnose it while the overheating is occurring because at any other time, things will look normal.
Rust and scale build up in the water jackets of the heads and block will interfere with coolant heat transfer to a degree, but if the scale dissolves and breaks off, it will plug a radiator/heater core.
This has the symptoms of a blocked radiator, but always diagnose first.
 

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Discussion Starter #10
So I will do some diagnosing on my cooling system but how did my idea for the fuel system sound . Run the electric pump from the secondary tank before the switching solenoid so when you start to car you switch to aux tank hit the fuel pump on and push fresh cool has back to the carb and lines, once it starts up you switch back to the primary and use only the mechanical pump
 

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The Chrysler solution, detailed in a TSB for some other Chrysler vehicles, for vapor lock was a low pressure fuel pump to supplement the mechanical pump. It was a complicated setup as it required safety precautions do the pump wouldn’t keep pumping if the key is on but the engine off.
 

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If you have 7-8psi mechanical, a 4-5 psi electric should work. At no time should it over pressure the mechanical. Do make sure that the lines to the pump will take psi as they normally have vacuum.
 

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Definitely a cooling issue. I second the motion on fan shroud, and also any missing ductwork that directed cold air to the radiator. IC is right, too - diagnose first.

Eesh ... The only real way to fix the cooling system, at this point, is to open up the block drains (not the sand core plugs) and get a decent flush mix, and flush it all out. You might even try Dawn dish soap as your final step.

Worst case scenario - pull the engine and take it apart. Have the machine shop give her a good bath. Put some 308 heads on it, if it doesn't have the W-2's. A good 2-row radiator will be fine.

Check exhaust routing. Check ignition timing and fuel > air ratios. Don't use aftermarket carbs, use the OEM Thermoquad.

The only real "heat" problems with the fuel system were: heat soak during warm restart in retail cars, requiring a carb adjustment, and the later squads were known to vapor lock, for which a factory retrofit kit was made available. You have a cooling issue which may be affecting the fuel system.
 

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Discussion Starter #14
Thanks everyone will check my radiator for clogs or something. Can I run like a 160 thermo or no thermostat hut with a restrictior wahser in it just doesn't the summer months or is that no no
 

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All changing the thermostat to a cooler one will do is slightly change when it overheats. If the cooling system can’t disipate the heat, and it can’t at times from your description, a cooler thermostat doesn’t help.
 

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All changing the thermostat to a cooler one will do is slightly change when it overheats. If the cooling system can’t disipate the heat, and it can’t at times from your description, a cooler thermostat doesn’t help.
Ok thanks I changed the radiator cao to a 16lb one and so far it's been fixed the old one we found out the part number was for like 8lb cap. I di have problem thiugj with the fuel pump with the electric on it just immediately starts dumping fuel down the carb through the boosters. And floods. How do I fix this
 

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Ok thanks I changed the radiator cao to a 16lb one and so far it's been fixed the old one we found out the part number was for like 8lb cap. I di have problem thiugj with the fuel pump with the electric on it just immediately starts dumping fuel down the carb through the boosters. And floods. How do I fix this
Psi???
 

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Check for sunk floats or bad needle/seat..
 
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