QuestionQUESTION: I own a 68' Spitfire MK3, I purchased it many years ago and have done nothing to the engine other than clean it, oil changes and replace the plugs. The car was modified prior to my owning it by placing a GT6 engine in it. It has ran very well since I purchased it although it is difficult to start when I take it out of storage in the spring.
This spring I could not get it started so I started looking at all the things I thought it could be. I replaced the points and condenser as they were very pitted. I then noticed that the carbs (Stromberg 150 CD's) were not receiving any gas, so I dismantled the carbs one at a time to check the floats and needle valve to make sure evaporated gas scum wasn't stopping gas from getting through the needle valve. This was not an issue so I cleaned and re-assembled..
Next I checked the fuel pump (note: the previous owner installed an electronic fuel pump)and it was working as I could hear it but the flow was very low when I disconnected the hose to the carbs. When I took it apart the rubber diaphragm was disintegrating and had many holes in it. Since I could not obtain a rebuild kit, I replaced the pump. I now have gas but the engine still will not start. When I crank the engine the plugs remain dry, I would have expected gas to appear if it turned over long enough and gas should drip out of the carbs if it flooded?
I know the fuel pump was defective and I know the points were badly pitted, but I do not know if the carbs are an issue or if since I took them apart they may require adjusting.
Long story but no clear answers...can you assist as to what I should try next?
Note: If I spray quick start in the carbs it does try to start.
Still feels like a carb issue?
ANSWER: Hi Norm,
When working in dealerships, I often received cars with that same story and I had to do the same on each one.
It sounds like you usually pull your own maintenance and that is good, however you are searching for the item that has made your car not run and that is not what you need to do. When an engine will not start you need to look at systems not items. All engines operate the same and only require 3 systems to run. Compression, Fire and Fuel. With conditions on each. It does not matter if the engine ran good last year, last week or one minute ago, the tests are the same and MUST be done and done in order with no stone left unturned.
First.-- you must be 100% sure the combustion chambers are correct even if it ran good one minute ago and not now. The only way to know is to run a compression test (compression gauges are not expensive if you don't have one) You want to see from 125 PSI to 165 PSI on all cylinders with very little difference between cylinders and be sure to run the tests with the throttle open.
Second. -- Then and only then can you proceed to "Fire" (ignition). Most people don't have a scope which can test the primary and secondary of the ignition system in seconds. But there are other ways to make rough tests to see if there is an ignition problem.
You should have all four plugs out from the compression test so take the plugs (if they look clean and dry) and put each on it's plug wire and lay each plug on a metal part of the engine and have someone spin the engine and you watch the sparks. You are looking for a thick blue spark (not is bright sun light). Thick is the size of a pencil lead and blue in color. A wire or thread thin yellow or orange spark is a weak spark. Then you should set the point gap and set the timing afterward. Check the wires in the cap to see that they are in the correct firing order and number one is in the correct position. (There is a quick method to do this by just putting your thumb over number one plug hole and watch the number one plug with it's wire attached and have someone spin the engine or you spin it if you have a remote starter button.
The compression will blow your thumb off of the hole with a "Pop" sound and if you watch the spark and listen you will hear the spark "Click". If the timing is close and the #1 wire is where it belongs it will seem as though the "Pop" is causing the "Click" of the spark. If you see hear it as "Pop-Click" or "Click-Pop" the timing is off. This is a rough method to see if we needed to set ignition timing first.
Third. -- Then and only then do we look at fuel. The starter fluid in the intake is a good test that you did. If you can keep it running with spray it is a sure indicator that fuel is the problem. If however, you can't keep it running with spray, then you may have missed something on compression or fire tests. Don't skip anything. Leave no stone unturned.
I didn't hear you say that you set the float levels when you had the carbs off. Also, were the diaphragms good with no holes.
Do your Strombergs have coolant operated choke or are they with the manual type?
These tests are 100% effective and never fail to find a problem on any engine.
Let me know.
Howard
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QUESTION: Thanks for getting back so quickly Howard, I appreciate it!
A few things I missed in my original note: The engine is a 6 cylinder, I did adjust the floats to 18MM when I had the carbs off and the diaphragms looked good.
The spark on the plugs are not blue as you mentioned, they are a bright white. (What does that suggest?)
The carbs have manual chokes.
I do not have a compression gauge so I will need to look at obtaining one.
Anything else you can add based on the above would be appreciated.
Regards,
Norm
ANSWER: That's right, you did tell me you had a GT-6 engine in this car which is 1,5,3,6,2,4 firing order but my GT-6 book says 19mm on the float setting for the GT-6. But that won't make that much difference. But I never seen a white spark in the shade before. But if it is thick that may not matter either but if you are close to a shop that has a scope it would be good to put it on the scope to check it out. Most shops here only charge about $35. for the ignition diagnosis.
But do go through all the tests I outlined first in the order I suggested.
Howard
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QUESTION: Hi Howard,
Looks like I have a problem!
I checked the compression as you indicated as being the first step and here is what I found........... First cylinder (Next to rad) was 150lbs, the next 4 were "0" lbs and the last was 90.
I went back again a day later and rechecked...........I know have "0" on all of them.
Is this possible or is my compression tool at fault? (I purchased a cheap one for 30 bucks.) I can't see how there could be such a variance between checks?
Thoughts?
Norm
AnswerCheck your compression gauge on a known good engine. (Be sure to have the throttle open when testing) (I never seen a 6 cylinder engine with -0- compression on 5 cylinders)
If the gauge is ok first check the valve clearance on all cylinders.
Howard
