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Diagnostic problem

Hi guys, I've been gone a while but I just picked this group up again.

One day several months ago I loaned my bug to my daughter for the day and something happened when she was out and about with it and almost didn't get it home. I'm having trouble narrowing down what's wrong. When the problem started the weather was crappy and I didn't have the garage space to roll it in so I put it off until things got warm. Then I was busy all summer and I'm just getting back to it. Along the way I worked on it a little here and there but not enough to really get to the bottom of the problem.

This engine has about 30k miles on it. I rebuilt it and had Dan Hall's machine shop in Portland do all the machine work. The compression is good and the oil pressure hasn't changed since the engine was first put into service. BTW, this is the engine that I used to refer to the perpetual project. It spent over 10 years in my bedroom closet waiting for me to get around to finishing it...

The engine cuts out a low RPM and gets worse as it warms up. By the time it should be warmed up enough to idle, it's running worse and I can't get to the back of the car to tinker with it. BTW the power is OK until it warms up then it hard to keep it running. Judging by the oil pressure, it never gets to fully warmed up before it's running like crap.

My first thought was the points and condenser were likely bad. I had the money so I put in an electronic ignition kit. It ran the same and I thought maybe it was fuel starving. Draining the gas gave an unimpressive flow rate so I pulled the tank and cleaned the screen. The screen was about half blocked so I figured I found the problem. Since I was in there, I installed an electric fuel pump and put a new fuel filter between the pump and tank. Still no change.

I've also been going over the electrical connections. I've been cleaning them or replacing them as required and packing them with dielectric grease. I've fixed all sorts of little problems that have had no effect on the problem.

There is a bit of soft soot inside the end of the exhaust pipe and while I don't see any black smoke, it does smell a little rich. right now I'm thinking it's either the carb or the coil is weak. Any suggestions?

Tony

Reply to
Tony W
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Tony, welcome back. check to see that the wire to the electric choke element is still connected and transmitting 12v to the element.... if it is, unhook the points from the coil, turn on the key and watch the choke element... it should be open fully in 3-5 minutes.

Reply to
Joey Tribiani

my first thought was stuck choke also. greetings from Gladstone!!

Reply to
Cletus

Valve clearance, you said the engine was rebuilt yes?

J.

Reply to
P.J.Berg

pull the spark plugs and tell us what they look like. Or take pics and show us.

Pull idle jet (or jets) and clean them out, as well as the passage behind them inside the carb.

Reply to
Jan Andersson

Check the heat riser piping under the intake manifold too. It has to get hot after the engine has been running for a few minutes. If not then it is probably clogged with carbon.

Do you have the correct spark plugs in it? How good is the spark? If it is too weak that might cause some running problems too. I have seen some aftermarket distributor rotors cause unusual problems. BOSCH only please!

What type of air cleaner do you have on that engine?

Just some random thoughts! ;-)

Reply to
dave AKA vwdoc1

I agree with this diagnosis. Most likely either the choke heating element is disconnect or otherwise not getting proper voltage when the car is started OR the heating element itself has burned out (i.e. open). If you have a multimeter you can see if +12V (or +6V if this is a 6V car) is getting to the choke. If it is, disconnect the wire to the element and measure the resistance of the heating element. I don't remember off the top of my head what the resistance should be (guessing on the order of 10 to 20 ohms) but it definitely should not measure open.

Reply to
Rusty Shackelford

I had to switch to eternal-september.org after Verizon dumped all news groups. I wasn't sure if I was going to take up news groups again but there was a few that I missed.

That was one of the things I checked today and it's good. Previously I couldn't get it to idle and the guys at the shop in Amity, OR recommended cutting off the end of the electric fuel cutoff valve. When I first got it on the road this was the only way to get it to idle but even before that it had great power from a little off idle all the way up.

This engine was out of a 72 Super before I rebuilt it. I set the valves today and they were a little tight. I'm worried that the valves could be cooked. I don't know what the normal compression for 1600 dual port is and I need to check it again now that I've ran it.

My fear is that I need to tear it down for a valve job. If that's the case, I won't get to it for a few more months until the winter motorcycle projects are wrapped up.

On the other hand my last engine was a 1600 single port just a little older than this engine and it ran great even when the compression was near nil. That engine was vandalized when some prick dumped dirt down my carb. The rest of the engine was fine but the cylinder were screwed. I almost gave up on the car after that incident.

Anyway the plugs were a little black and wet but not like it was running massively rich or dumping raw fuel down the manifold. I warmed it up pretty good today and it was too hot to work on when I gave up. I'll look at the plugs again tomorrow. I also tried it with and without the stock oil-bath air cleaner removed and there was no appreciable difference.

Tony

Reply to
Tony W

Re the choke heater element. The end of the element itself is riveted to the cover. Those rivets can get loose and you get a poor connection. If you get a narrow punch ~ 1/8 inch diameter you can just get it in gently past the element and with a few LIGHT taps tension up the rivet. Recovered a few that way. John

Reply to
John

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