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351C engine problems


egon1107
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Hello,

 

first to my car. I have a 1973 Mustang Mach 1 with an 351 Cleveland 2V and a manual 4 speed. gearbox.

 

Problem:

I have the problem that when the car is warm it suddenly turns off. Not while driving but when i drive along and then stop for a street sign or cause of traffic as soon as i press the clutch at first gear like 10 sec later the engine turns off. Sometimes when i quickly start again to not block the traffic it runns normal but especially when the car is very warm from a long trip the engine turns off every time. So i have to rev the at about 1500 to 2000 rpm when i stop in traffic to keep the engine runing.

 

Engine:

The engine was rebuilded 2 months ago, so i drove like 1500 miles since. I have a small edelbrock carb with 600cfm (edelbrock 1405). I have a very street use cameshaft (Speed Pro cs1085r) so normally it revs at about 800 rpm very smooth. I have a standart HEI Distributor from summitracing (sum-850025) which is vaccum advanced. At this point i was not sure but i connected the vaccum advanced port to the Manifold Vaccum Port of my carb (right port at edelbrock). The ignition is set to 8degrees BTDC.

 

I already tried to play a little bit with the ignition timing to set 6 or 10 degrees but nothing changed. Than i was reading that this could be a problem when the spark plug cables are crossing each other so i sepperated them with a minimum of 1inch gab everwhere to go sure but nothing changes.

 

Does anyone have the same problem or knows how to handle with this ?

 

Thanks Daniel

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Its sounds like its on the spark side can you try a different coil? 

Throw some more timing at it later like 14-16, but figure out why its cutting out first.

Remember 1 train wreck at a time.

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These can be difficult to track down, a lot of variables.

On the carburetor side, idle speed, idle mixture, float level, vacuum leak, fuel percolation from over heated carburetor, stuck EGR, bad fuel.

On the electrical side, coil breaking down when hot, component in the HEI breaking down when hot, bad connections, including bad grounds, timing.

Engine side, vacuum leak, low compression (bad valves), PCV valve, exhaust crossover on intake manifold too hot due to restricted exhaust on one side.

 

 

“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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As you seem to note it is heat related, I would look at whether the fuel might be boiling off in the float bowls. I'd consider a spacer under the carb like this

 

https://www.jegs.com/i/Canton-Racing-Products/074/85-152/10002/-1?CAWELAID=230006180000876335&CAGPSPN=pla&CAAGID=44693592161&CATCI=aud-391543084240:pla-176568833831&CATARGETID=230006180039218595&cadevice=c&gclid=CjwKCAjwrqnYBRB-EiwAthnBFsLB4RQd5ma5WkGKB9X_xb3sRcHXijGfg-k0aMpNxlocuQImpvdxCRoC5nQQAvD_BwE

 

You can combine it with an aluminum heat shield and you will need longer studs https://www.jegs.com/i/Holley/510/108-70/10002/-1

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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There is quite a long flow chart in the Ford manual for this symptom if you can get hold of one. A systematic step by step elimination of causes. It is based on Ford equipment not your aftermarket.

David

When a man is in the woods and talks and no women are there is he still wrong??:P

David

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My advice is to get a fuel pressure gauge. Install the sensor as close to the carb as possible. You need to confirm that you are getting fuel pressure when the issue happens.

'Mike'

73 Convertible - 351C/4V CC heads/4bolt/forged flat tops/comp 270/rhodes/mallory unilite/tri-power/hookers/glasspacks/c6/3.50 limited slip/Gear Vendors/Global West sub frames, strut rods and shelby style traction bars/ Rear sway bar/tilt steering (not original)

 

Pics of modifications included in: [button=http://www.7173mustangs.com/thread-1973-convertible--3335]My Garage[/button]

 

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My gut tells me fuel percolation, especially since you have an Edelbrock carb. The one piece base & bowl design is notorious for heat soaking and boiling the fuel. Install an isulating gasket or spacer and let us know how it works out.

 

 

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Thanks for your Help.

 

I got a 1inch carb spacer out of plastic, but nothing changes. I tried it a whole afternoon but i have the same problems. The engine was very hot and i touched the carb which was hand warm. So the spacer does his job.

 

Unfortunately i have not the chance to get another coil or ignition system. I just can by a new one but my installed one is nearby new and when it works perfektly byside the single situation. So i dont really think that the ingnition is broken.

 

I dont have an EGR on my engine and i dont think the Fuel is bad. In Austria we have quite good fuel, i dont now if you know but it is unleaded Super Plus 98 octane what i get from the gas station.

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First thing I'd check is if there is fuel in the carb when this happens. Maybe try to (with engine off) remove the airfilter and move the throttle to see if fuel squirts into your carb. I think will e's idea to check fuel pressure is a good idea as well. It could be heat soak (air bubble in fuel line caused by heat) and maybe the fuel pump isn't strong enough (anymore) to get fuel through quick enough.

 

With the engine hot, will it continue to idle if left for 10 minutes?

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I allredy order a fuel pressure gauge but it will not come before next monday so i have to wait. But your suggestion with the air filter of is a good idea.

 

It depends, sometimes when the problem occur i immidiatly start cause i am in traffic with like 10% throttle and then it idles like there were never any problems. But sometimes i have to start it 4 or 5 times and everytime i go off the throttle and it comes like under 1500 rpm it turns of.

 

When i give him some time like 10-20 min it idles very smooth.

 

Edit:

I remember a modification i did after the rebuild, i custom made a new downpipe and wraped it in a fiberglas  fabric band to pretend to head up my floor and inner space. Dont know if this has an impact.

 

 

2018_04_03_13_53_32.jpg

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Have you checked to see if you have spark when the engine dies? Checking for fuel squirting is the other thing to definitely check.

 

You need 3 things for the engine to work: spark, fuel, and air (and timing). We can dismiss timing to a good degree, and probably air flow. Start from the basics and go from there.

 

My personal opinion is that the coil is going bad due to heat soak. But checking for spark and fuel will rule in or out that idea.

Let me check your shorts!

http://midlifeharness.com

cactus.jpg.92e5d9d8700abc0ed60c8ccb3426248e.jpg

 

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@midlife

 

I can understand you and i will check fuel pressue. How would you check the spark? How can i check the spark a few seconds before this happens, after it turns off i turn the starter and the engine starts after like 5 sec so no long starting, it starts nearby instantly like a warm engine would.

 

When the egine runs there is no problem but its just when i drive and then stop from driving the engine turns off. Most times after starting again it all works at idle and driving, so i am not sure becuase when the coil has a problem there will be more impacts at driving or idle and not just from drive to stop.

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My two top suspicions are coil failure and fuel percolation. The coil gets hotter driving around town and in stop and go traffic due to lack of air circulation. When you re-start it you are applying the full 12 volts to the HEI, instead of the reduced voltage from the ignition/coil wire, which could overcome any weakness in the HEI/coil.

 

Fuel percolation can be the result of high carburetor temperature, or high fuel line temperature between the fuel pump and carburetor. High temperature in the fuel line can either expand the fuel or vaporize it, forcing fuel past the float valve.

 

 

“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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The other thing that I would ask is does it do it when you stop briskly as opposed to when you stop easily? It could be the rear jets coming uncovered due to hard braking, in which case extensions would help greatly.

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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Checking for spark: use a timing light or backyard test: Pull a spark plug and wire, place wired plug close to metal and crank the engine. You should see a nice blue spark. Be careful and don't hold the plug while doing this!

Let me check your shorts!

http://midlifeharness.com

cactus.jpg.92e5d9d8700abc0ed60c8ccb3426248e.jpg

 

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I read your first post and I think the problem you have is being caused by a float bowl level that is too low.

I do not think that engine temperature has anything to do with the issue, nor do I believe the issue has anything to do with ignition problems.

Here is what I believe is happening....  When you first start the engine cold the fuel pump fills the bowl enough to start the engine and allow it to idle properly. As you drive the rpm rises and the engine starts pulling more fuel from the float chamber, which is fine as the pump is flowing more fuel at the elevated rpm and provides just enough fuel to run but eventually the float chamber gets to a point where .. when you cut the throttle back, disengage the clutch and the engine goes to idle then there is not enough fuel in the chamber to keep the engine running and then it dies.. When you try to restart the engine the pump then gives it a splash of fuel enough to start.. and the whole process starts again.

As long as the engine is above idle it will pull enough fuel to run because of the pumps elevated speed.. as soon as the rpm drops the engine drains the chamber.  This is not a fuel pressure issue.. is is caused by a incorrect float level and it needs adjusting.

 You are perceiving the issue is heat related because you only experience the issue after the engine has run for a bit.. and the engine has had a chance to warm up.

 Now keep in mind this is just my assumption from past experience and from your initial comments and I could be dead wrong.

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  • 2 weeks later...

Sorry but i didnt have time for the car the last days.

 

Yesterday i found some time and tried the sings you suggested.

So when it happens i dont have fuel pressure, but the fuel pressure is back as soon i try to restart. My fuel pump is quite new with only 500 miles on it as well as the carb.

At normal conditions i get about 5psi of fuel pressure, seems correct because the spezifications of my fuel pump are 5.5 to 6.5 max pressure.

I replaced the fuel line from the pump to carb because it was squased a little bit with a heat protection 3/8" one.

 

@sonnerbilz It is possible that at a brand new carb the float bowl level is not correct ?

@midlife As i checked the spark works perfectly after it happens.

@jeff73mach1 It happens wenn i hard brake as well as when i stop very smoothly. Most times when i go from driving to stop this occurs, no matter if i hard brake or stop as smooth as i can. As soon i press the clutch engine turns off.

 

As i tested i discoverd that it happens more when the engine got some resistance at stopping. This means when i have the light and my extended fan on the alternator has to do some work and it happens far more. As well as i turn the steering wheel instantly after stop the power steering is a little resistance it happens more often so it might not be the battery voltage.

 

But i tried a full charged new battery to get sure and still the same problems.

 

Thanks for your time

Daniel

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It's very likely that the float level is wrong on a new carburetor. New never means it is working properly or adjusted correctly, on any car part.

 

 

“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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Are you using an electric fuel pump? How is it wired if you are? How do you know the fuel pressure drops? if you have a gauge mounted is it electric?

 

The more I think about it the more I suspect something simple, like an electrical issue.

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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It's very likely that the float level is wrong on a new carburetor. New never means it is working properly or adjusted correctly, on any car part.

 

+1 to this. Never assume it's not your new parts.....

 

 

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I've had a few new Edelbrocks, and I remember just one of them that didn't need adjusting out of the box.

 

 

“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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