Probably a fuel system problem

October 1, 2008 | By Richard Prince


I’m from the old school—carburetors and spark plugs are my thing—and I am having a problem with computers and electrical injectors. I have a 1993 Bronco and am installing a 1990 351 cid engine along with a wiring harness out of a 1995 F-150 that had an unknown engine.

Installing the engine and harness was easy. The Bronco’s fuel tank was full of garbage and what looked like varnish. I replaced the in-tank fuel pump, cleaned the fuel tank and lines, and replaced the fuel filter.

But when I started the engine it would not stay running. Eventually it would not even start up. I think the fuel injectors may be dirty and stopped up. I have spark. I do know that the 1990 351 engine ran when I pulled it out of a truck and then installed it in the ’93 Bronco two days later. The ’93 had been stripped and its wires were cut up.


There could be a lot of different reasons why your engine refuses to start and run properly. Since you have spark it is logical to conclude that the problem is somewhere in the fuel system. It is most likely an issue of clogged injectors or insufficient fuel pressure.

You mention that you cleaned the Bronco’s fuel tank and lines but don’t say whether you did this before or after starting the newly installed engine.

If you attempted to run the engine before cleaning the fuel system then you likely delivered a load of muck to the fuel injectors. If you cleaned the fuel system (and did a thorough and good job of it) prior to starting the new engine then the problem is probably not due to dirt clogging the injectors.

Are you using the correct fuel pump for the engine/fuel-injection system that you’re now running?

If the pump in the truck delivers insufficient pressure then the engine will run very poorly or, if the pressure is low enough, it won’t run at all.