I have a VP 5.0 with TBFI, and I'm trying to pinpoint my fuel injection problem. My fuel pressure guage reads about 30 psi when cranking, so I think the fuel pumps are ok. I pulled the connectors and put a test light to them and one side of each connector was getting constant power once the key was on. The injectors are not spraying fuel when the engine is cranking and no fuel is coming out of the small tube that points down towards the throttle body. Can anyone tell me what the next logical step would be, or should I just send the whole TBFI out to be rebuilt?Thanks,Pat
Thanks for the reply. It is a 1999 5.0gi. I cannot hear the injectors operating while cranking, just the fuel pumps. Fuel injection is pretty new to me. Shouldn't they be spraying fuel as the engine is cranking?
As I recall, the fuse in inside the little plastic box mounted on the front of the starboard exhaust riser. When you say connectors, do you mean the ones that clip to the injectors? If they have power then it's not the fuse. The injectors are supplied with 12 volts at one wire by the fused circuit, and the other wire is grounded by the ECM to fire the injector. However, the ECM must be receiveing a reference signal from the ignition module. If this reference signal is not being recevied, it could be due to several things. It may seem unrelated, but is the engine getting spark? Check for spark as this can help with the diagnosis of the problem.Dave
Engine is getting spark, starts with starting fluid or carb choke cleaner in manifold. The connectors I checked are the ones that clip onto the injectors. Should fuel also be coming from the small tube that points down into the throttle body? I'm wondering if it could be bad fuel or clogged fuel filter.
Probably not bad fuel or clogged fuel filter. If this were the case, it would start, but run poorly or stall at higher RPM. You observed that the injectors were not firing, yet you had fuel pressure. Focus on that for now. ok,You got sparkYou got fuel pressureYou need to find out if the injectors are being triggered. You said that you had power at one wire of the injector connection. Can you hook up your test light to the connector again, this time don't connect the ground clip of the test light to the battery or engine ground, connect it to the second wire of the connector. Then crank the engine and the test light should flash. Does it?Dave
Don is right about using caution when doing this test. It would be better to use a test light intended for this purpose(sometimes called a "noid" light). You can find them at just about any auto parts store, and they are not a lot of money (about $10.00). You will need one for a GM TBI system. If possible, pick one up today and use it for testing tonight.Dave
As I understood, you just have a basic multi-purpose test light. It should be ok, but there is no way to be 100% sure. Especially if it's a cheapie. A "noid" light is only for testing injectors. It looks like this: Dave
Pat,The problem would appear to be in the throttle body or the injectors. I just realized (reread earlier posts) that you had the throttle body apart. So it's hard to say what exactly is wrong, but the problem sure seems to be in the throttle body/injectors. It occured to me that one possibility is you may have accidently swapped the fuel pressure and fuel return lines when installing them on the back of the throttle body. But thats just a wild guess.I don't know if I can help any more than that, but post any additional questions if you have them!Dave
Dave, Thanks, you've been extremely helpful. I'm sure I have the lines on correctly. I probably screwed something up when I was trying to take it apart and clean it. Any idea where I can get a new or rebuilt one for a decent price?Thanks again
Have you checked to see if any fault codes have been set? Do you have a manual? You also REALLY need to find the serial number. Things do change from year to year and all this guessing isn't going to help if they are guessing about the wrong engine.
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