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Great weekend for cruising here in Connecticut so we took the VS Speedster out Friday night.  After about an hour, I noticed it running up near the "warning" level of the temp gauge.  Heading for home, it started popping, bucking, then finally fuel starved and died.

My first thought was the Seafoam I put in the tank last time I filled it broke some crap loose and I had plugged carbs (dual Webers).  I continuously sprayed carb cleaner in the carbs as my wife cranked her.  After quite a while, it back fired a couple times and started to rev.  Maybe just because it cooled off a bit?  Any way...got it home safely.  Took her back out yesterday with a full tank of fresh gas and the exact same thing happened.  She's now back in her garage and I'm going to start diagnosing.

A couple things I'm thinking:

  • Remove and clean the carbs (this situation has never happened before so I'm leaning toward this as the issue) - Have never done this so any suggestions would be great.
  • Relocate the fuel lines and filter away from the heat of the heat tubes and fan shroud
  • Adjust valves (maybe too tight?)
  • Rejet the carbs to larger jets?

Yes, my engine seals are in place, and the compartment is pretty well sealed up.  Oh, the car is a mid-late 90's VS with an 1835.

Thanks for your thoughts!IGor Pro Photo

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  • IGor - VS Speedster
Original Post

Well, again, we don't really know the true temperature without sticking a candy/meat thermometer down the dipstick tube, but is this something new or has it done it in the past?  If it's something new, then I would start looking at the fan to see if there is something like a paper towel in there (see Mike Pickett's post of last week) or a mouse nest in the fan or on top of the heads - a Bore Scope from Harbor Freight would help a lot here.   Get one with a light.

https://www.harborfreight.com/search?q=bore%20scope

I sounds like classic clogged jets.  It backfired because you had been pumping the gas and loaded up the muffler with raw gas from the accelerator pumps which, after a while, got ignited and BLAM!

I like your first fix - rebuild the carbs with lots of blasts of carb cleaner), but find your fuel filter(s), too, and replace them with new ones.  It/they may be clogged.

Don't think #2 is necessary if it hadn't been doing this last season, maybe move the fuel lines if it is obvious they're getting hot (but again, if it was OK last season, skip this step),

#3 Yes, check the valves (should do that at the beginning of each season, anyway)

and skip the #4 re-jetting to a larger size altogether - Again, if it was OK last season, why mess with jetting?  Jetting doesn't change over time - They just sit there.

That's my 2¢.

You've got my cell from the NE Speedster list.  Call if you need help.

Last edited by Gordon Nichols

Awesome, thanks Lane and Gordon - nice hearing from you guys!

The only time I ever had anything similar to this was in Carlisle at the Speedster meet.  The car was running really rough and popping.  SOC came to the rescue with a little in-field carb cleanout.  I didn't have the overheating and dying out issue ever before though.

So, since I did just run Seafoam through it, sounds like the most likely is some crud loaded up in the jets?  If they are clogged, I'm assuming that would also run him lean and cause overheating, true?  I have a great VW mechanic up here locally, but it's really time I get into doing the carbs myself (I have, after all, had this car for 10+ years!

Thanks again for the responses and support.  Looking forward to Carlisle next year!

One odd thing to look at.....  I worked on a car that'd run well for quite a while and then started dieing after a spirited run in warm weather.....  Cause was rapidly diagnosed as fuel starvation.....   Input to mechanical pump was good, output, not so much.....  Obviously needs a new pump.....   New pump installed and same thing....  WTF!!!!

Side of the road pump removal reveals the push rod in the extended position and it doesn't change with engine rotation....   

Turns out the phenolic part that heat shields the pump and guides the push rod had evidently absorbed oil over it's life time and, with heat, closed the bore enough to grab the rod.....   Walked across the street to the local ACE hardware with the block, and "tested" a 5/16 in. drill bit on the bore.......  Reinstall the pump and it was still on the car when sold 2 yrs. later when it sold......

 

It sounds like what's new is the overheating.

If the gauge goes much higher than is normal, or certainly close to the red, you should probably stop, pop the engine lid, and let it cool.

When the car cooled down, it ran OK until it overheated again and then started popping and breaking up?

If so, your fuel pump is OK and the jets are clean. Blocked jets won't cause overheating, but a hot engine compartment will cause vapor lock, popping, and an engine that doesn't want to run.

I'm guessing if you solve the heat issue, your 'carb problems' will go away.

Is your fan belt worn, loose or slipping?

 

@ Danny...thanks Danny, I'll check them out.  I went with electronic ignition a couple years ago.  Let me look at the coil.

@ Mitch  As for the questions, yes, I always pull right over for a cool down, but these were pretty immediate loss of fuel, then died.  I never let the car "fully" cool down to see if it would run ok after as we were on the side of busy roads both times so I went with the "spray the piss out of carb cleaner in both carbs until it fired" mode just to get it off the road.  After it fired up, it ran well at high speed for another 10+ minutes until we were home.  It's never happened before and I did just put Seafoam in the tank so I'm betting it released some crap into the carbs.  Oh, I did also replace the fuel filter with a glass one.

Thanks guys!

@Bobby D posted:

I have had two Manga-spark dry pack coils go bad on me.  I wasted a lot time messing with the carbs and distributor thinking they were the cause.

Bobby’s comment reminded me that after I swapped out my regular distributer and coil with the then new Magnaspark I had the same problem you’re describing. The car would run great then sputter, cough, choke, and die. After about 10-15 minutes it’d fire right up and go a short distance then start the process over again. Changed to a new coil and, voila, the problem was gone. 

Last edited by Robert M

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