Please help. While driving my car the other day it just died. I had to call a tow truck. After getting it home here is what I found. To start I have a 350 TPI that has only 2000 miles on the recent rebuild. I have replaced the TPS and IAC. After putting the scanner on I noted that I am not getting any injector pulse. I have fuel at the rail, the fuel pump runs, and I have checked for spark and the car cranks. I also checked the fuses and everything looks good there as well. I have heard that the VATS module can be a problem, but it is expensive. Is there a way to test to determine if it is the problem or is it hit and miss when replacement is required. I am sort of at the end of my rope and need help (other than going to the dealer who will probably soak me).

 

isn't there a relay for the injectors? no power to either side? sorry no idea how to check VATS

 

Does the car have spark?

 

Yes there is spark, fuel, and the security light goes off on the dash. I am not sure if it is VATS related or not... very perplexing

 

Also if it were the injector relays, where are they located??

 

that is very perplexing indeed, i'll look into it and try to help... do you have any codes in the computer? Have you scanned it?

 

also, is there no pulse on either bank of injectors or is it one side?

 

Thanks for the help... I am really stumped. I have scanned the computer and did not get any error codes back. When I indicated that I wasn't getting injector pulse that was from the scanner. It never left the 0.0 range. I did hear and note readings for the fuel pump, so I am quite certain that is functioning properly. I have heard that the fuel pump relay even though operating can still cause problems.....

Do you think that vacuum leaks would cause a problem this severe???

 

That would require a massive vacuum leak.

There are no relays for the injectors that I am aware of. There is a start interlock/enable relay in the VATS system, but that should also prevent operation of the starter.

Injector pulses are controlled by the ECM alone, and if the VATS conditions are not satisfied in the ECM, you'll get no injector pulses.

One thing you can do is test fuel pressure to be sure the system is functioning at proper pressure, instead of just delivering fuel at some unknown (and possibly low) pressure.

Have you tried to manually add fuel to the engine for starting (carefully, of course) ? You can also briefly ground the ECM side of the injector harness to fire all the injectors and see if the fuel is what you're lacking.

There are two fuses for the injectors, located in the interior fuse panel. Make sure those are both intact. You should be able to measure 12VDC at the injector harness when the ignition is ON.

This should be interesting.

 

Thanks Vader,
I have checked the fuses and everything checks out. I think you may be right about the ecm. Going over some of the service manual documents I noted that they seem to be pointing to either a problem with the ecm or the prom chip. This car was origionally a 305 and was upgraded to a 355. I put a stock 350 chip in it from the same year. I will go through the flow chart / checklist and figure out if the ecm is alright and then continue on to replace the prom back to the origional 305 prom. Hopefully one of those two items is where the problem is.

 

For the ECM to do its job, the connections must be intact. If it can't read the distributor reference pulses, it will not fire teh injectors. You may have pulses at the HEI module but not back at the ECM. And since the ECM switches the injectors to ground, you need reliable grinding at the ECM.

You might try to unseat and reseat the ECM connectors a few times to clean the pins, and make sure the PROM/CALPAK is seated fully.

 

Yes Sir,

I hope to get home tonight and do both of the things that you identified. The distributer connection is a very good point. I pray this is the only reason that I am having difficulties. Otherwise it will be back to the drawing board. I will keep you posted!!! (no pun intended)

 

I know this is an old post but i am having the same problem with a tbi car . sometimes my injectors pulse and the car starts, and runs and drives fine , and other times the injectors will not pulse. what did you find that caused your problem?

 

WOW someone replied to my post. I was sure this topic was a dead one. Fortuneately I think I resolved it. I had just installed a new 355 in my camaro and I knew the injectors were probably small for the heads and cam that I was using. I received a set of 24# Ford SVT Racing injectors just after the vehicle died. I actually assumed the computer was the culprit. However after installing the new injectors the car fired.

Alright here is what I figure the real problem was. The car had been sitting for quite a while before the new engine went in. There was a ton of black carbon build up in the intake. I used some throttle body cleaner to brake some of it loose. I figure some must have blocked some passages in the intake and possibly even the injectors. I pulled the intake and washed it all out in a varsol tank (squeeky clean). I also cleaned out the intake runners.

At first I thought my scanner would pick up an injector pulse while cranking. I was wrong (I think). You will not register an injector pulse while cranking the engine. They only pulse after it starts.
All you might need to do is clean out your air intake system (carb??). Your injectors may also be clogged. If it is still running I would try some injector cleanner (strong strength) and drive it out. I am not an expert, but that might be the cheapest answer to start off. Hope this helps.

 

here is the deal with this car ...... (not trying to hijack your thread ) car will start fine 10 -15 times in a row then all of a sudden no start , injectors stop firing but there is fuel to the throttle body(tbi car). if I pulse the injector with my tester it will fire and the car will try to start . I have fixed all the other problems with the car but this is a pre-existing problem(about 6mos old).I have replaced the ecm , prom, ignition module , and fuel pump relay. the connector at the relay is melted and the wires are questionable? but the fuel pump is priming and i'm getting fuel all the time . the car will start and run fine ,never stalls out. but sometimes when you shut it off and try to restart the injectors just stop firing? I am doing all of this work as a favor for my wifes friend and I don't like the fact that I am looking like a monkey!!!!sorry I think I hijacked your thread anyway