Could it be a overheating coil..?

-
67cuda360

67cuda360

Well-Known Member
Joined
Nov 11, 2009
Messages
462
Reaction score
23
Location
St.John's NL, Canada
Can a overheating coil create unregular drops in fuel pressure or do I have multiple issues at work?

I've been having a stumble issue with my 360 which only happens when it is really hot outside.

Last night I took the car for a drive and on hard acceleration it suddenly bogged like it was getting no fuel, lay off the throttle and everything is fine. (car also doesn't feel as strong in hot weather).

First I thought it was some kind of vapor lock, but then yesterday I noticed my tachometer needle was erratic at idle (only lasted 30 seconds or so), which made me think something is wrong with the coil.

When I checked my fuel pressure at idle it read 5psi but then suddenly dropped down to 2 and then quickly came back up again.

Could all this be caused by a bad coil?
My coil is a chrome accel unit that pretty much sits on a bracket and rests on the intake, I can only assume that it gets pretty HOT :)
 
It is very possible the coil is going bad. I had a few coils over the years go like this, alot of times you are better off moving the coil to a little cooler location.
 
I agree, I moved mine to the firewall and installed it upright instead of on it's side. I don't see a coil messin with your fuel pressure though. Do you experience a sudden whoosh of air when you remove your gas cap when the car has been driven?
 
It is a stock replacement fuel pump, less than a year old. There is no fuel pressure regulator anywhere in the system and it supplies the edelbrock 650 CFM carb with a steady 5 psi of fuel pressure. The pressure only starts fluctuating on really hot days and the drop in pressure is very irregular.
 
Very similar issue here. New fuel pump didn't cure it. I can leave the fuel door open and see no change. The air in my see-thru fuel filter is making me crazy.
 
RedFish said:
Very similar issue here. New fuel pump didn't cure it. I can leave the fuel door open and see no change. The air in my see-thru fuel filter is making me crazy.
Click to expand...

Yep I hear ya.
my see-thru fuel filter show air when warm as well. Apparently it is normal though and most people just say to switch over to a non-clear filter so you can't see the air LOL.
 
the high temp is making your fuel flow less,, im assuming you have stock size fuel line ?? first i would insulate the fuel lines in the engine bay,,cooler fuel flows more volume,less starvation,,also a thick carb base gasket made out of fiber, or insulator material will help,, i would consider a after market mechanical fuel pump,if you have any mods to the motor,,,
 
yes my car has the stock size fuel lines and it also has a large phenolic spacer under the carburetor to insulate it from heat. There is definitely no fuel percolating in the bowls since I never have a problem starting the car even on very hot days.

The fuel line to the pump is a metal line of which I have insulated the section directly beside the exhaust manifolds (has rubber fuel line around the metal line). The metal line from the pump up to the top of the engine block has the same rubber fuel line wrapped around it. After that it is just rubber line to the carb. The fuel pressure gauge is tied into the rubber line just before the carb.
 
If you keep finding air in your fuel system, have a look at the rubber line at the tank.

Even a tiny crack in that line can let air in - and never drip a drop of fuel.

I had a ford with the line on top of the tank - out of view. It would do all sorts of odd stuff. If you let it idle long enough the carb bowl would go dry. You could drive it all week without a problem. At idle, the fuel pump could not move enough fuel foam to get the job done. Above idle it was adequate. So at a stoplight the fuel level was creeping down. You could "run out of gas" with a half tank. Same thing happened if you stayed in it long enough it would starve too. Replaced the fuel pump twice chasing that one.

B.
 
As we speak, I'm in the middle of installing a "vapor return" sytem.

Either install (solder, braze) a 1/4 stub into the tank, or up in the fuel fill tube.

Run a 1/4" tube along the fuel feed line back to the tank.

Throw away that "see through" filter and buy either a 33040 (5/16) or 33041 (3/8) wix filter which has a vapor return orifice/ port built in. Install the filter either vertically or horizontally with the 1/4 port on the UP side and hook it to the tube back to the tank.

Take a REALLY good look at your fuel line. On my 67, in the area near the torsion bars, the line comes pretty close to the headers. I'm planning to install a metal shield hooked to the stub frame to separate the line from the headers

There IS a possibility that you have an electrical problem, but the only way this would cause the fuel pressure to drop is if the engine idle deteriorated enough, as in almost dying.

More and more we are seeing problems with the bulkhead connector, and drop across the wiring harness. The general path is from the start relay, through the bulkhead, ammeter wiring, connector at the ignition, through the switch, back out that connector, back out the bulkhead.

That's really a lot of area for problems. Check your voltage drop by turning key on, engine OFF. Put one probe on the battery pos. post, the other on the "dark blue" from the key/ bulkhead supplying run voltage to the ignition/ regulator.

You should see LESS than 1/2 volt, way better is just a couple of tenths.

I recently did some rewiring on my 67, and eliminated the bulkhead connector. On mine, there was a ONE VOLT drop with this test. On mine, the bulkhead connector was a "mess."
 
the rubber hose isnt a insulator,,,, black conducts heat,,, u need insulating material,,,, or a shield blocking the heat,,,a shield is mounted along rather then around the object,,,,that stock pump cant move enough volume in the high heat,,,
 
fstfish66 said:
the rubber hose isnt a insulator,,,, black conducts heat,,, u need insulating material,,,, or a shield blocking the heat,,,a shield is mounted along rather then around the object,,,,that stock pump cant move enough volume in the high heat,,,
Click to expand...

Ah, okay so I may have made things worse :)
I'll have a look what I can find online. Any insulating material that you would suggest?
 
ive never had that problem,,,but ive come close too it,, ide look at summit or jegs,,speed way motors and see what thery offer,,,or any type of foil lines pipe insulating material maybe at your local home improvment store,,,but look at jegs or summit first,,,, or do a google search on fuel line insulating,,main thing is make sure its away from heat,,,exhaust,,and not laying on the intake
 
3/4 split loom for wiring will create a dead air space around the fuel line. It blocks the engine heat from the line without transferring heat to it.
 
RedFish said:
3/4 split loom for wiring will create a dead air space around the fuel line. It blocks the engine heat from the line without transferring heat to it.
Click to expand...

Hi RedFish, can you elaborate. I'm not sure what you mean with the above. It sounds very interesting.
 
split loom for wire harness ect.. is available at part stores. If it is larger than the tubing it covers it will create a dead air space inside.
I dont know if it will be a great help. Couldn't hurt.
 
sorry to jump in but this is happening as we speak](*,)<allow time differance to uk lol>my {440ci / mech fuel pump/msd 6a ign and single point dizzy}starts no probs, drive and when give it some bogs down and dies.the other night i couldnt get to start at all when broke down,felt like a fuel starvation problem despite me seeing fuel spray into carb primaries when throttled .i suspected the msd/coil so 10 mins ago byepassed the msd returning the car to run on points and it run fine,re connected the msd and............it run fine. i think all i can do is take for a drive, give it a little and be prepared to get caught out,then when its all hot and bothered and wont start swap the coil to see if works,then bye pass the msd.......and finally pour some cold fuel into top of primary carb to fill bowl and see if its fuel starvation/fuel vapourizing etc...........its a frustrating one as dobt want to take anywhere thro fear of getting stuck
 
67cuda360 said:
Can a overheating coil create unregular drops in fuel pressure or do I have multiple issues at work?

I've been having a stumble issue with my 360 which only happens when it is really hot outside.

Last night I took the car for a drive and on hard acceleration it suddenly bogged like it was getting no fuel, lay off the throttle and everything is fine. (car also doesn't feel as strong in hot weather).

First I thought it was some kind of vapor lock, but then yesterday I noticed my tachometer needle was erratic at idle (only lasted 30 seconds or so), which made me think something is wrong with the coil.

When I checked my fuel pressure at idle it read 5psi but then suddenly dropped down to 2 and then quickly came back up again.

Could all this be caused by a bad coil?
My coil is a chrome accel unit that pretty much sits on a bracket and rests on the intake, I can only assume that it gets pretty HOT :)
Click to expand...

Read my thread that I created to ask for help.... look at post number 7

I would recommend reading the entire thread because it was a nightmare and had a lot of great advice from other members.

I wish I could tell you exactly what solved my problem but Im just not sure. I do know that after installing the Griffin aluminum radiator, shroud, and putting a sever blade mechanical fan on there it solved the problem AS WELL AS REMOVING ALL THE TRASH OUT OF THE TANK......... LOL. The Carter fuel pump was not working very well also.... a stock unit worked much better. When you are losing fuel pressure I kind of doubt it has to do with the coil. The number one thing is when you first start the car while cold pop the hood and watch the fuel pressure gauge. If it starts to drop when the engine is hot then you need to find out why. I would throw something on, change something around and then fire it up and watch the fuel pressure. When the fuel pressure drop the engine would go lean resulting in shutting down or running very poorly. Make sure you have the idle mixture set on the "rich" side. Float level adjusted properly and all that good stuff.

http://www.forabodiesonly.com/mopar/showthread.php?t=59704&highlight=fuel+pressure

We'll help you get it straightened out.
 
I've tryed everything I can think of and I still have the plastic filter filling and emptying in cycles.
 
You'll always get some of that if your pump is weak. As the needle valves open, fuel is allowed into the carb draining the line. As soon as the valves close (because the carb bowls are now full) the filter will fill again. I had this problemn with the old stock pump because the diaphragm was being eaten up by the new crap the pawn off as gas. I'll bet you also see a bunch of black crap floating in the filter.
I installed a new stock filter with a diaphragm designed to work with the new gas and voila, no more black crap and much less air in the filter.
 
You must log in or register to reply here.
-

Back
Top