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Engine woes. Where to start?


Trevor571548534737

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Don't put a carb on it. Huge disadvantage in CMC.

 

I disagree, Maybe in CMC but not CMC2. My numbers now are 262 / 300. And I like to think I was competitive at Hallet.

Bob

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Don't put a carb on it. Huge disadvantage in CMC.

 

I disagree, Maybe in CMC but not CMC2. My numbers now are 262 / 300. And I like to think I was competitive at Hallet.

Bob

 

You were.

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We had an issue early on in our car where we would be good for a couple of event weekends and then it would start to run crappy by stumbling and misfiring a little bit and eventually we wouldn't be able to start it because our battery was dead. We thought the battery was the issue, so we threw a new battery at it and it helped a little, but it would eventually happen again. We thought it might be the alternator, so I had that one checked for free at Autozone along with a couple others I had laying around to make sure they were good. Once the counter dude figured out how to hook up the wires, he tested them all as good. Well, the dude must have been a dufus 'cause we continued to have the problem and when we took the alternator out again and had it tested at another local parts place where they actually knew what they were doing, it was bad. A fresh new alternator fixed it all. Whatever was going on, the electrical components on the fuel injected Fords seem to like a good voltage.

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replaced 2 injectors, fpr, and rail. he car started right up, and at least idles like a champ, it revs up proper and seems fixed. I am going to have to go find an autocross, or drag race t&t before gingerman. Thanks for all the help.

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The legal Ford cams, especially in CMC, are not very good with a carb. Is anyone running a carbed 5.0L Ford in CMC-2?

 

Not yet, but soon.

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This car is driving me insane. The car starts right up, and runs, and drives fine. BUT ONLY if I spray starting fluid in first. No ether no start WTF!!!!

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Also the fuel rail I have on the car now is a replacement I bought off a local guy, and is got no schrader valve. (wtf?) So I guess I am going to have to rig something up to test fuel pressure.

 

From my own personal experience - many moons ago, I purchased a used fuel rail + feed lines, and put it on my car during the process of an engine swap. When it came time to start the car, I couldn't keep it running. Jacking up the FP to 100+psi (:o) helped get it started, but it wouldn't stay running.

 

Swapping back to the original fuel rail and feed lines fixed all the problems. The used set I bought had some clog/restriction - they were summarily destroyed, and thrown away.

 

Given the car won't start unless you spray ether leads me to believe you have a fuel supply issue. Fuel pump, fuel filter....

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Yes, before I sprayed the starter fluid in I took the plugs out to check spark, and the 4 I checked had fuel on them.

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This is a bit of a hack of a suggestion, but try holding the gas pedal to the floor if you think it's flooding while cranking it. This will actually turn the injectors off during cranking (or maybe it does something similar, but it magically seems to work). Just remember to get your foot off the gas pedal when it finally does fire, though. I had to do this with the old turbo setup in my 1994 GT when hot-starting it, as it wouldn't want to restart after turning it off and going into 7-11 for a couple of minutes, etc.

 

Mark

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Weird.

 

The car starts right up, and runs, and drives fine. BUT ONLY if I spray starting fluid in first. No ether no start WTF!!!!

 

Old gas? Is the gas "just" old enough that it won't start combustion at starter revs but will burn once the engine is running?

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I have this pinned down, but I don't know what would cause it. The injectors have 12v in the run position, and while cranking. However they do not pulse during crank, but they DO pulse after the car starts. That is why the thing will start with ether. The only thing I can come up with is the computer is bad? any ideas always welcome.

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I have this pinned down, but I don't know what would cause it. The injectors have 12v in the run position, and while cranking. However they do not pulse during crank, but they DO pulse after the car starts. That is why the thing will start with ether. The only thing I can come up with is the computer is bad? any ideas always welcome.

 

Crank or cam position sensor?

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I have this pinned down, but I don't know what would cause it. The injectors have 12v in the run position, and while cranking. However they do not pulse during crank, but they DO pulse after the car starts. That is why the thing will start with ether. The only thing I can come up with is the computer is bad? any ideas always welcome.

 

I assume you are working on a fox Mustang, A9L style computer. A good way to check if the computer is able to output the 5Volt reference signal. Look at the TPS three wires. Black is ground, should read 0 volts to chassis, orange is the 5Volt reference to the black and to chassis, the dark green should be about 1 Volt with the key on, engine off. If this does not check out, there is an internal ground on the computer circuit board that will open if too much current was pulled. Any chance an automatic oxygen sensor harness was installed in a 5speed car? I did that and blasted this ground trace as soon as the neutral safety switch is activated....oops

 

The injectors should have 12Volt, with the key on, engine off. The ground side of the injectors is the switched side. During cranking the duty cycle is high for a short period of time, like a choke on a carb it dumps in fuel. The duty cycle is less when the car is running. If you are using a normal meter, the duty cycle is the inverse because the ground is the switched side and most meters assume the 12Volt is switched. Although, I would not worry about checking the injector firing, unless the driver is out of the computer, it is firing the injectors if it passes the 5Volt ref test above. A simple way is to put a finger on the injector body, you can feel or hear the pulsing.

 

There are three important grounds, one at the computer harness to chassis, one on the injector harness to engine block, and engine block to chassis. Check these again.

 

You do have everything the same as far as injectors, 19lbs injectors, mass air for 19s, and a computer for 19s? The three must match, same for the Cobra 24# stuff.

 

Chuck

TX CMC#14

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Thanks guys. It turns out I had a bunch of (little?) problems. As mark suggested my damper was spun, and timing was off. Thats why it ran like garbage. ALSO, the TPS was jacked, and that is why it wouldn't start.

 

I had a bad fpr, tps, crank damper, starter, and battery. I hope my luck changes from here out!

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