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Engine running badley

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GeorgeB

GeorgeB

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I am a new member and now own a Sprite MK III (HAN8L, 1098cc) for the second time. The 1st time I owned one was in 1965 for 4 years and college was more important than the MK III; really missed it. Now I have another one and it will require a lot of work. As I start back into owning this one I am asking for some help. I have set valve clearance, new plugs-Bosch Super Plus 7999, new points and condenser for 25D4, static timed, synchronized and adjusted SU HS-2 carburetors, and new fuel & air filters. When I go for a drive the engine backfires & sputters now and then. The engine also seems sluggish, not much get up and go and sometimes when I come to a stop and put the clutch in the rpm drops and the engine quits. Car is positive ground and positive lead on coil is going to CB at distributor. Any ideas what's going on? Thanks.
 
Welcome George! and welcome back to the fold. Cars need fuel air and spark. You've pretty much replaced the spark parts so I would turn to air and fuel.

My first guess is fuel. You say it sometimes quits (ie. not always) and describe the sputter and sluggish. First thing I would do is check your fuel tank - you get an astonishing amount of crud in that many years. It is not uncommon for the flow to be interrupted. After that check the fuel pump though most of the time it works or it doesn't

My second guess is air. I would check your vacuum lines and then whether your carbs need rebuilding. The shafts wear and it is difficult to maintain the mixture.

Only check one thing at a time, don't ask me how I know.
 
I had an intake gasket leak on my 67' that made it have a mind of it's own, stalling at lights, high idle at lights, sputtering, hard starts when warm etc... just a thought
 
Compression check?? could be lots of things. Had some of those symtoms with a head gasket leak.

Kurt.
 
Could even be dirt in the float bowls.

Check the easy, cheep stuff first.
 
Welcome to the funny farm GeorgeB! have you checked your dashpot oil?


m
 
I am going to go with air leak.

How to check. Moss has a few videos on their site showing how.

However, I just spray a bit of carb fluid at the ends of the throttle rods, and the manifold gaskets with the engine running. It it all of a sudden goes well you found it.
 
George -

Where in West Chester are you located? I live in Liberty Township and have a warehouse in West Chester where I store/work on my toys.
 
Satisfy an old mans fancy and check the points gap please.

I know, I know, you just fitted them. but......
 
This kind of problem could be any number of things. Start with a few quick, easy, and obvious checks: dashpot oil, fuel in the float bowls but no wet fuel in the intakes (i.e., no flooding), hot spark at the plugs, no air leaks around the throttle shafts or intake manifold. If something seems amiss from these tests, focus in on it and see why it's happening. If you have a weak spark, for example, check the points and condenser. The condensers available these days are crap; see my investigation of this in the Wiki. Look for signs of arcing, especially around the rotor. If the cap has a carbon center contact, be sure it is still there. Be sure that the plug wires are OK. Most of this is obvious.

If the spark is OK, go to the carbs. 90% of these problems are crud in the fuel, float valve stuck open or shut, or air leaks. If the mixture adjustment is way off, that could do it too, but it would have to be pretty far off to cause as much trouble as you describe. Also, sometimes things come apart in the jet assembly (e.g., some SUs have little cork washers that deteriorate), and the carbs need to be rebuilt. If that hasn't been done in a long time, it might be a good idea just to rebuild them anyway, and while you're at it, check the shafts for wear.

It also sounds a little like vapor lock. Is this worse on hot days?

Most of this is just logic--eliminate possible problems until you focus in on the one that is really causing the trouble.
 
Looks like I will be busy with all the suggestions I have received in one day; thank you everyone. Some of the things that have been asked to check I have already done. I will do again and keep all of you posted on progress. Also I have ordered carburetor kits and throttle shafts. Plan to recheck gap on points tonight.
 
George -

We are practically neighbors! I live off of Hamilton-Mason just on the other side of 747. Right across from where Homarama is going on. My shop is behind Lakota Plaza on Cin-Day. I will send you an e-mail.
 
Okay, the first thing I did was recheck the points gap. It was at .015. Next I used Berryman's carb cleaner to check for a vacuum leak at the carburetors and all around the carburetors. No change in in engine speed; RPM's remained the same. Next I revisited the 25D4, pulled it and checked everything at the bench. All seemed well. I still could not let go of thinking there was something wrong with the operation of the 25D4 so I pulled the the drive gear from the engine. Went to TDC and reinserted it at 2 O clock. Went to 5-degrees BTDC for static timing and rechecked twice. The engine runs well, sluggish performance and backfiring was eliminated. Could it have been 180 degrees out? However, after I run for awhile and everything thing is at run temp (not before}, the engine sill dies when I press in the clutch. I will now rebuild the carbs and check the inlet gasket for leaks. Any other thoughts? Thanks.
 
If it was 180 out it wouldn't run - spark at wrong times
 
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