Hey everybody,
My daughter's 93 jimmy with the CPI system won't start. It will fire if I use starting fluid, so I have ruled out the ignition system. I have already installed a new fuel pump, a new fuel pressure regulator and a nut kit from the junkyard. The old nut kit had a split in one of the plastic lines. I need some help troubleshooting this problem. What else should I be looking at? Could the whole injector unit be bad? If so, how do I test it? Are they rebuildable? I am amazed at how much plastic car parts cost! Please help.

 

When you replaced the pump, did you replace the fuel filter? Did you clean the ground wire and mounting area before you reconnected it?

 

The electrical connections are all solid. I can hear the fuel pump buzz for two seconds when I key up the ignition. NO, I did not change the fuel filter(because I'm such a cheap b**tard) I'm going to the store right now.

 

It's required when you change the pump. Let us know what happens.

 

well, I just got done putting on a new fuel filter. The old one didn't look too old, and the fuel that came out was actually not bad either. Jimmy still won't start. It fires for about one second, but won't stay running.

When I put the new fuel pump in, I did install a new pick-up screen as required by the warranty

 

did you check your fuel pressure?

 

Having a fuel pressure gauge is standard test equipment for these CPI engines IMO. If you test at the valve, back of engine, inline with the nut kit line, and there is operating pressure then the problem could be with the injector voltage. There is a set of wires, red and blue that lead into the plenum, you probably saw them when you had the plenum off. There is a connector on the outside of the plenum, it should be possible to test that connector for signs of voltage. Can't give you any specifics on the voltage or testing but I am sure with a little searching you can find something on this. If the fuel pressure and injector voltage all checkout then it seems likely that the injector unit is faulty. Although I have never done it, I have read where the spider unit can be tested before you close up the plenum. Putting the poppets in a container and cycle the injector should give you an idea if the CPI unit is working. As far as I know there are no rebuild kits for the injector unit, but rebuilt units can be bought at a cost savings.

 

If the pump buzzes for only 2 seconds, then its holding its pressure Im assuming. I think you should reach down beside the EGR valve and tug on the red&blue wires that poke into the front of the intake. The connector on top of the injector has very fragile wires up inside that are like hairs, and a rubber gromet on it thats probably eroded away. You may wanna try pulling those wires and if it will fire, then you need to replace that connector, dont be cheap and go buy the new connector for a whole ten bucks at the parts store and be done with it. If they are unable to find the part you want, then ask for the injector connector for a 93 fullsize 5.7, its the same part. IMO this part should be changed anytime you are messing with the injector unit.

Here is the white connector we are talking about


And here is where the problem will be, up inside the 2 holes is the hair like wires that contact the top of the injector, they are supposed to be paralell to one another, if you look into yours, you will probably see that one is crooked and making bad contact with the injector pins... Just cut the wires OUTSIDE the intake, and solder the new part on. You see this is the new part, and there is a rubber gromet that keeps the connection from shaking around... That rubber part is probably gone on your daughters truck cause rubber and fuel dont mix, the new one will be silicone.

 

awesome! Thank you everyone for all the great info. definitely going to get myself a pressure test guage. Good info on the connector at the top of the spider too. I really do need to quit being so cheap especially since this is my kid's car and I would hate for her to be staranded somewhere cuz her old dad is a cheap skate. I'm going to get busy on this tomorrow. Again, Thanks everyone, I'll update tomorrow!

 

I have read all of the replys to your question and all sound like great answers. I just had to replace my spider injector (re-manufactured one's will save you about $100) after I replaced my regulator and found that the injector itself was bad. You can check these injectors by removing the plenum, and one by one, pulling out the poppetts and cycling the fuel pump. By doing this, you are checking to see if fuel is spraying out of each line. I recommend disconnecting the coil wire from the coil, or distributor cap, thus preventing the engine from firing.

Also, when you changed your regulator, did you make sure that you used a pick tool and removed the old o-ring from the injector (in the whole the regulator goes into). One other thing, when you changed your nut-kit, did you cycle your fuel pump to make sure that you got the lines back into the injector completely (which can be a pain). You may have fuel leaking from there which will prevent it from starting.