Hello, all. I have a 1990 Ford F-150 EFI. The engine turns over when the starter is engaged, but it does not catch.

Any ideas as to what could be causing this? Spark? Fuel? My guess is compression is just fine.

 

Well, First off...Welcome to Ford Trucks!
Stick around and you will find lots of info here in past threads and a lot of member who will help you out.
Well, I'm not an expert, but you should be checking the things you mentioned. You are probably right in that it has nothing to do with compression.
Do you have spark & fuel? First things you check for.
You can check fuel pressure at the Schroeder valve at the back of the fuel rail( on most engines..if not all), usually on the passenger side. It will look like a air valve on a bike wheel. Check your spark at your wires. I would start with that and post back.
Some others members here will be able to give you some more ideas, as you diagnose your problem.

ps...always give as much info when posting a problem....such as the engine in question for starters.
All the best

 

The way I like to check for fuel problems is to spray gas in the intake, if it suddenly works then chances are that's my problem.
I'm not sure how these computers work on these engines but when you hit the gas trying to give it more fuel (if you think that is your problem) it go's into a clear flood mode, so dont' bother; but I could be wrong, as I said I'm not sure though.

 

Are you saying to just spray a mist of fuel into the throttle body?

 

that's how i do it-but the pressure test is safer and tells ya whether the fuel pumps are working if ya get good fuel pressure and spark-then it could be the injectors-then ya check for injector pulse-a little electric jolt that tells your injectors to spray-can be done with a noid light or a voltage meter

 

do you hear the fuel pump when you cycle the key?

 

First off what engine & transmission do you have?
What do you mean by catch?
I take it you are trying to say it cranks but the engine does not start.
Is this what mean by catch?
If so as dustybumpers above said when you turn the key to on do you hear the fuel pumps run for one second and then stop?
Or do the fuel pumps run all the time the key is on?

If the selected pump does not run for one second and stops or at all do you hear a click from the relay on the drivers fender when you turn on the key?
If you hear a click when you turn on the key do you hear it from one relay or two relays on the drivers fender?

If you hear the selected pump run for one second and stop you will need to check for spark next. Stick a long screwdriver in the end of one of the spark plug wires and while holding the handle have part of the shaft near the the engine and have someone crank the engine and see if you have spark.
OR
Go to an auto pars store and buy a spark tester and check for spark, this is the best way.

If you have spark and the selected fuel pump runs for one second when you turn on the key you need to get a fuel pressure gauge and put it on the fuel rail at the Schroeder valve and the valve is located on most engines on the drivers side near the front of the engine.
Turn the key off and on about five times and see if you get about 38 PSI pressure.

Post back what you find and you will help you more when we get this information.

 

Damn. Why buy a Chilton's when you have subford? Lol just messing that was a very informative post