Re: How to test a coil and a fuel pump

Posted by Tim Cole On 2015/6/21 15:49:26

I use an oscilloscope these days to look at waveforms.

For this case there isn't a lot of data.

I would do a warm compression test just to make sure the motor can pull the fuel.

Next, I would do a good old fashioned pump test using a vacuum/pressure gauge. As well, pump capacity into a bottle running with fuel line disconnected. You can use a T fitting with rubber hose and line ends. I love my homemade tools.

For ignition, why not get the car into misfire mode and keep it there as long as possible. Then kill the ignition, coast to a stop, and look at plugs. If the plugs are white/clean then it's a fuel problem. If they are sooty then it is ignition.

The gas cap thing is a good case. Take the thing off and road test the car. If there is an air leak in the lines the cap may be aggravating the situation.

You can test a coil on the road using a scope, but a an adjustable spark tester from NAPA may help with a low voltage problem. Another test is using a dwell meter. If the dwell is changing with RPM there is slop in the distributor drive.

Hope this helps.