QuestionQUESTION: This past summer I got my 74 midget running after 22 years of storage. Within one day it went from running well to not being able to start at all. Here is a brief rundown of some of the things that have been done to it. The engine was rebuilt but never started prior to storage. Head was shaved 0.060, weber carb purchased, cam machined. Fast forward 22 years... fuel system cleaned (much sludge in tank); clutch slave cylinder rebuilt; Mallory dual point distributor installed; new (22 year old) carb installed; got the thing started and it was running very rough which turned out to be an intake leak at the manifold. After fixing that things seemed to be pretty good. I had it to the point where I just had to bump the starter and it sprang to life. It has 10 miles on it since getting it running just zipping around the neighborhood. After taking it to the gas station and putting premium gas and a lead additive in the tank it went down hill throughout the day. Here are the things that have been checked 1) tried regular fuel 2) checked manifold for additional leaks 3) checked cylinders with compression gauge 4) visually inspected ignition points and checked gap 5) disassembled carburetor and checked for clogging 6) replaced condenser 7) replaced coil with Mallory coil, instructions state that I need to add a ballast resistor if not equipped and I am not sure but I don’t think mine has one. I did not check the time gears/chain
I am reaching my wits end and any advice would be greatly appreciated.
Thanks,
Andrew
ANSWER: Hi Andrew,
Working on problem cars in dealerships and shops I never found it productive to target any component.
All gas piston engines require just 3 things to run. Compression, fire and fuel. With conditions on each.
1. Compression must be from roughly from 125 to 165 PSI
2. Fire (spark) must be a strong spark and be close to the correct time.
3. Fuel must be a combustible fuel and be available to the spark plug.
1.Every car I get that either don't run or runs poorly I do a compression test (throttle wide open)
2.In shops where I didn't have a scope, I would pull a plug, place the wire on the plug and lay the plug on a metal part of the engine and spin the engine with the starter and put my thumb over the plug hole. This causes a "Pop" sound as the engine spins. You can see the spark (not in the sun light) jump the plug gap. It must be thick and colored blue. (Sometimes you can hear it "Click") When the timing is close enough to start the engine it will seem as though the "Pop" is causing the "Click" or visually the spark. But when the timing is off enough to make it hard to or not start, it will sound like "Pop-Click" or "Click-Pop". Then I knew to set the timing before proceeding.
3. Fuel needs to be roughly in the correct ratio to air and available to the plug. First with the air filter off the carb, spin the engine and put your hand over the carb to confirm that you have vacuum then spray a fuel like WD-40 or such into the intake while spinning the engine. If it tries to start for a second or two then your problem is the carb, fuel supply or such.
Each time you make a test like this, you isolate the problem it a sector. Then you make further tests to isolate that sector smaller. Until you find the fault. Using this method you will always find the fault.
Run these tests and let me know.
Howard
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QUESTION: Thanks for the quick reply. I completed the compression test. I did it with the throttle open and I have two readings the first reading is when the needle first jumped (one piston cycle) the second reading is when the engine was cranked for several seconds and the reading topped off. I am assuming the first reading is the correct reading and the second is the result of some compounding, please clarify. Here are the results.
C1 85psi 160psi
C2 80psi 150psi
C3 90psi 180psi
C4 85psi 170psi
Again thank for the help,
Andrew
ANSWER: Several seconds or at least 4 or 5 revolutions with the throttle open is the correct method as you can see. Even though your readings have a lot of spread 150 to 180, it will run good with those readings. In a shop, we would do a wet test after that to see if the 150 cylinder would come up. (Wet test is to put or squirt about a teaspoon of engine oil in each cylinder to see if readings would exceed 10 to 15% more than the dry first readings.
Now it is time to do the rest of the tests I suggested.
Howard
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QUESTION: Howard,
I conducted the other tests. The pop/click test yielded positive results so I went on to the carb test. A few observations; placing my hands over the intake stacks proved that there was vacuum. When I removed my hands a significant amount of gas dribbled out of the intake stacks. Turning the key produced enough of an ignition to disengage the starter motor but it never actually fired to life. The plugs are wet when I take them out of the head. It seems that too much fuel is being dumped into the carb. Ever since it has not been running, there has been gas leaking at the seal between the carb and the intake which has o-ring seals and spring washers to dampen vibration. As I stated earlier the carburetor was purchased twenty-two years ago and never used until this past summer. The fuel has always been filtered before going into the carb. When I disassembled it to check for clogging everything looked good. The apparent excessive fuel issue existed prior to disassembling and reassembling the carb. The carb is a Weber 40 DCOE. Again, thanks in advance for any suggestions you may be able to provide
AnswerWetting the plugs is an indication there is not fire or it is weak. Dry the the plugs and spin the engine a while with the plugs out to dry the combustion chambers and replace the plugs and with the choke off spray starter fluid in the intake to see if it starts. If it does not start fix the ignition. It has to try to start on starter fluid if you have ignition and compression.
