I know that this is a truck site, and I've got a '93 F-150, but I also have a 1985 Crown Vicoria. This car is a potential demolition derby car. Everything is gutted and ready to go but the 5.0l engine in it has trouble staying running. It is carb injected and the injectors are working fine. My question is why wont it stay running for longer than five seconds? It will fire up but then it will die all of a sudden. It only stays running if I play with the choke and throttle at the same time. I have checked all the vacuum lines and have looked through a repair manual for a possible diagnosis but I have come up short. If anyone has an idea to what might be going on, please let me know. Thanks in advance for any help.

 

Carb injected? You mean CFI throttle body fuel injection? Looks like a two-barrel carb with injectors right over the bores? I'm confused, because these didn't have a choke.

Possibly you removed a sensor that's needed to keep this thing running properly, or you have a fuel delivery problem. But I'm not sure about running a CFI system in a derby car. A good impact that damages part of the control system could knock you out early. I'd yank the throttle body and all injection engine controls off and stick a two-barrel carb on, it'll bolt right to the manifold. You might have to use an aftermarket electric fuel pump designed for use with a carb though, as some of the CFI systems are high pressure and the CFI pump wouldn't work with a carb. Even the low pressure systems are still too high, about 14-16 psi where a carb needs about 3-7 psi. A FP regulator might cut that down enough.

Another possibilty occurs to me...did you remove and bypass the Inertia switch in the trunk? If not, you may have triggered it while working on the car and aren't getting any power to the fuel pump. It definitely needs to go away if you do stay with the CFI system, or the fuel pump will shut off the first time you take a hit...or hit someone else.

How long do you have till the derby?

 

Tiger Dan, I am sorry about the confusion before. The Crown Vic is throttle body fuel injected. I must have heard wrong from one of the guys I had helping me. So much for diesel mechanics working on gas engines, lol.

I was wondering about your idea of replacing the throttle body and all injection stuff with a two-barrel carb. How much do one of those normally run new/used? We already have an electric fuel pump attatched becuase the stock in-tank fuel pump would not work outside the tank. The fuel kept it cool inside the tank. Outside, it was getting way too hot.

And by the way, the earliest derby we have entered isn't until June 17, so we have some time to work with the problem.

 

June 17th! Talk about planning ahead! I used to leave everything till the last minute and spent the last week or so burning the midnight oil to get the car finished in time!

Okay, it's pretty much what I thought. CFI or TBI...Throttle Body Injection. Ford calls it CFI for Central Fuel Injection. I have one on an '84 Town Car I'm stripping down.

I'm still curious about the "choke" though...

So what are you using for a fuel pump? If it's an off-the-shelf aftermarket unit designed for use with a carb, then it's not supplying enough pressure for your CFI. I'd have to look it up to be sure but I think yours is the high pressure CFI which needs around 40 PSI.

Anyhoo, you could pick up a 350 or 500 CFM Holley used, the 500 should go for about 100 bucks (around here anyways since it's the designated carb for almost all classes at the two local tracks) and you could probably pick up a 350 CFM for 50-75 bucks. Another alternative, one that might find for free, is the Motorcraft 2bbl that came stock on so many Fords. Look for one on an early '70s 302, so it's already jetted pretty close.

 

To tell you the truth, we were all ready to put this car in a derby last winter until this happened. June 17 was the next closest derby that we could find around Cincinnati. Last race, we too did some last minute fixes and almost went in without brakes. I would have gone without but the rules required them.

About the choke, that is what our diesel mechanic said. When he was working with it, he was playing with two different things under the hood while I was in the car starting it for him. I'm not to familiar with this kind of thing, although I do know how it works and operates. You might be right in saying that there is no choke. I think that he should probably stick to his diesels, lol.

For the fuel pump, we went to Carquest and bought an out of the tank electric fuel pump. I believe that this is producing enough pressure becuase we are getting fuel to the injectors and it fires up everytime we try. Does that mean anything?

Thank you for all of your help so far and for any more that you might wish to add.

 

Some external electric fuel pumps need to be mounted below fuel tank (cell) level, because they don't provde enough suction to draw fuel uphill to keep a running F.I. system primed. Have you replaced your fuel filter? I always place a filter between the tank and pump, especially in a "gravity fed" situation, 'cause that's where the crud is gonna go.

 

Yes...but is it a high-pressure pump for fuel injection, or a standard electric fuel pump for a carb? If the latter, it could supply just enough fuel to the injectors to get it to start, but not enough to really keep it going. What's your fuel pressure? There's a Schrader valve right on the throttle body to test it. Should be 39 psi if it's a high pressure system (which I think it is.)