QuestionMy 1975 Triumph spitfire is having issues starting when its hot. When I say issues I Mean it just wont start. It turns over and You can smell gas after trying to start it for a few moments. I already installed an inline electronic fuel pump but it didn't fix the problem. Any tips?
AnswerHi Jacob,
I learned early working in dealerships that when you have a car that don't start to clear your mind of any possible cause and forget symptoms and run tests.
Test systems first not parts. There are only three systems that an engine needs to start and run. Compression, Fire and Fuel. They must be tested in that order too.
In your case testing the compression MUST be done hot as that is when it does not start.
You should see from 125 PSI to 170 PSI on all four cylinders. The test MUST be done with the throttle open. If you have less then 125 on any cylinder you need to run a second "Wet" test. A "Wet" test is done by squirting about 3 or 4 shots of engine oil (about a teaspoon of oil) into the plug hole just before the compression test (throttle open)
The "Wet" test will produce a higher reading then the first test but it should be no more then 10% to 15% higher. If it is not higher and the first test was low you first need to adjust the valves. If that does not bring up the compression and the "Wet" test did show a lot higher you have a ring problem.
If the compression was good with the engine hot and in a no start condition you need to test ignition. We had a scope to run tests in seconds but most people don't have that equipment but there are simple tests that can be done with only hand tools.
Remove a spark plug and place the plug on the wire and lay the plug on a metal part of the engine and place your thumb over the plug hole and have someone spin the engine over as if to start it. The compression will blow your thumb off the hole with a "Pop" noise and you need to watch the plug spark at the same time. It should seem as though the "Pop" is causing the spark. The spark is a "Click" but if you see a "Pop-click" or a "Click-Pop" then the timing is a little off and may cause the hard starting. The spark should be thick as a pencil lead and colored blue (not in bright sun light). If the spark is thin like a hair and yellow or orange it is a weak spark.
If you have no spark remove the coil wire from the distributor cap and either hold it about 1/8 inch from the head and spin the engine and watch for a spark (thick and blue).
If the compression is good and the spark is good you now can test fuel. This is an easy test all you need is a spray can of starting fluid from any auto parts store. Spray it into the intake when trying to start it. If it starts right up, then you have a fuel problem.
A compression gauge and a spray of starting fluid are not expensive but useful tools in diagnosis. You must do the tests in the correct order and when you establish which system has failed there are different tests for each system so let me know which system has failed and I will give you that system's tests.
This method of diagnosis is a 100% method of finding a failure in a system. Then when the system that failed is identified the next step is to identify the failed part in that system.
It is too expensive to just start replacing parts in the hopes of hitting the failed part.
let me know which system has failed and I will give you the next set of tests.
Howard
