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351w/ carb/ MSD- loss of power/ dies!! Help!!
Got a problem....I have a 351w, holly carb/ MSD. Initially had problens with car having loss of power when driving an hour or so.(would stall, but regain)..when car got hot, would be hard to restart..strong smell of gas when finnaly would get restarted...have seen gas burp out of front bowls......was told to check fuel pressure, I added a regulator..., was running at 4.5 PSI, I did bump up to 6.5, PSI, ran fine for about a month of weekend driving...took car out this past Sat, drove for 10 miles, immediately died...took a while to start, had to get back home limping along at a fairly higher rpm.. (still tried to studder)..fuel pressure reg showed 0 psi while motor was running (???)..got home...wouldn't restart, tons of gas getting in carb...huge back fire...help! Electrical problem? Fuel? Lost for words.
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Next time it won't start/run. Turn it off, remove the air cleaner, look down the carb, fully open the throttle and see if fuel squirts in. If it does, fuel is not likely the problem. If there is no fuel, then fuel supply likely is the problem.
When my MSD failed, it would start and run cold, and it had enough juice to run hot until I shut it down. Then it wouldn't start until it cooled. I'm sure there are other failure modes too. |
Thanks Tommy, I did try that, fuel squirting in nicely, very wet inside...in fact, in starting the car, appeared to dump too much fuel in the carb (white smoke trickels from side pipes). I am wanting to lean towards an issue with starter witch, but can't make myself believe that would have any bearing....unless it wasn't firing at times.
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What are the sight glasses showing in the fuel bowls when its running and having problems. Start with a clean fuel system, clean filter and two new needle and seats. Tons of gas getting in the carb is usually needle and seat or very high fuel pressure overpowering the needle and seat. Replace the power valve also.
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I did pull the sight screws, both are right at the line..have not replaced needle and seat yet, was trying to avoid that as I really didn't want to mess with the settings and have to re-tune that carb as I have read that is more difficult...I did pull both bowls off earlier to air clean the ports etc...very clean inside..car has 13k miles.
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fuel percolation or vapor lock, maybe both.
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had a similar problem, piece of small gasket got between the needle and seat. took off needle and seat, cleaned it and everything was fine. Set float so it was level when float bowl is upside down, that will get float level very close to what it needs to be, that should put the float about half way between top and bottom of bowl.
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I had a similar problem that took me months to track down because I kept tellingmyself it was carb/fuel. Turned out it was the MSD coil. Would run fine for awhile, then run rough or die. Replaced the MSD box - no change; replaced the MSD coil - problem solved. I was using their heavy duty vibration resistant coil, but it still failed. Also, be sure you mount coil vertical and away from heat; mine was bolted to the front of the head on my FE; I put a 1/2 inch insulator between it and the head after I replaced the coil and confirmed that the problem was fixed. It's been about 10 months now without an issue.
Hal |
I would wager that you used some Teflon tape on your fuel lines/system someplace!!!!!!!!!!
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Agree with Vector1 that vapor lock is the most likely cause. Is fuel boiling in bowls after you stop and let it sit for awhile? To address this problem, get some reflective insulation from McMaster-Carr and insulate all fuel lines in engine bay. Make sure none are touching a heat source, like an oil line. Then insert a phenolic spacer between the carb and intake, and maybe an aluminum heat shield too, all with extra gaskets. For me, the spacer and insulation fixed the problem with summer gas, but with crappier winter gas I needed to add an aluminum shield for radiated heat.
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I had the same situation as Tommy - it would run fine, but if I stopped
for gas I would have to push start it - it wouldn't even turn over but would start easily on a slow roll. Sent the MSD box to El Paso and $38 later got it back. No issues since. |
All of the above answers are good and one of them likely is the problem. It would take some space, but have you considered running your gas line through a cool can?
Ron |
Can you list what MSD parts you using?
Fuel pressure gauge read zero, is the gauge liquid filled? My bet is you have an ignition coil failing. |
Teflon tape particals in needles----------
Fuel pressure 4 1/2 ???????? add regulator, raise pressure to 6 1/2????a regulator can only lower the pressure, not raise it--too many basic fuel system factors here and even if the ignition is bad, it won't correct the fuel supply problems----------this will ( as in most mal treated ignition/fuel issues) end in an engine fire---------- |
Probably a fuel issue- but Check the timing.
I put in a new MSD distro and did have a MSD distro gear issue. Kept chasing what I thought was a valve issue as a I was sure the car timing was perfect since I set it. Essentially the car timing was changing as the gear wore down. Saw all kinds of weird things happen. http://www.clubcobra.com/forums/pict...ictureid=13357 |
I've had two MSD coil failures, different symptoms each time. The first time, very rough idle and backfired when starting out - ran fine at rpm under load. Idle got progressively worse until it wouldn't idle at all. Replaced coil - problem solved. Second time, it just died and that was it. Easy roadside repair. So, even if your current problem isn't the coil, I recommend having a spare coil in the trunk since they do fail.
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I too have lost two MSD coils. Both failure modes were similar. Breaking up at higher rpm (>3000). Progressively gets worse until it quits. Now when I get the same symptoms I just replace the coil first. Always carry a spare. A lot of O'Riely parts places carry the coils.
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