I bought a noid light and it acts exactly like the injectors. In crank it wont light up except for as im letting off the key it will light up bright and if i start it with the carb it will light up just fine

Meaning that the injectors are fine

I also checked for spark during crank with my timing light. I am getting spark during crank

I have been keeping a little notebook of what I have done so far, here it is.. I cant really think of anything else to check.

1. Test power at INJ terminal during crank. Power with coil disconnected 8.5V
- Power with engine running 13.5 v
-tested power on white inj1 wire and red inj2 wire

-power in RUN but engine not running, 11.5V

Conclusion. Power to inj. is good, either injectors faulty or ecm not sending ground signal.

2. Check power to fuel pump during crank. Method: disconnect oil pump safety switch and crank with coil disconnected
Result: 8.5 Volts during crank

3 Hooked up TBI unit with fuel line connected and one injector plugged in.
Results: Same as noid light

4 Found crank signal pin C9, probed ECM plug for power, power at C9 during crank is 5-6 volts

5. Tested with noid light, explained above

6 tested for spark. Results above.


any ideas on what now?

Pablo

 

The injectors should be firing while the engine is cranking.

Then you first crank the key the ecm may skip a couple DRPS, but then the PWs are fairly long, and then decay to shorter PWs.

If you aren't seeing the moid flash during crank, that's a problem.

At this stage, I'd say try another different .bin, and then another ecm.

Will it start with a shot of ether?.

 

I have tried a different ECM (forgot to put this on my list i have two 7747s) and different proms.

Yes it will start if i get fuel in there and run just fine. I didnt use ether but once or twice that last shot of gas as im letting off the key was enough to start it. From there it ran great. Just wouldnt give fuel in crank

like i said, the injectors act just like the noid light

 

It seems as though there is a bad ground. Maybe the wire from the Battery - post to the fender, or some ground strap from the engine to the firewall. Maybe an ECM ground to the engine block (all ECM grounds are to the engine).

This is why: #1 & #2 (in your first post) state that at crank there is 8.5 volts.

Then in #4, crank signal at ECM, there is 5-6 volts. That is 2.5 to 3.5 volts down from cranking volts at the engine. That is a significant difference.

For #1 & #2 you probably had the voltmeter ground on the engine someplace. For #4 the voltmeter ground was probably the ECM, maybe dash panel(?).

Measure the voltage drop, during crank, between items such as the engine block and the fender (and/or firewall), and battery - and engine block. Also measure the voltage drop between battery - and ECM case (during crank).

Try other areas, someplace along the way I'll bet there will be a significant drop. If not on the ground side, then on the power side.

When the injector + was checked, was the injector in place to provide a load? Loading a circuit during testing is important.

This post isn't meant to be a do-this and it'll fix it, I'm just trying to get some ideas out.

RBob.

 

When you say test the voltage drop do you mean use various different places as a ground for the DMM while testing the voltage?

When i tested the crank pin on the ecm i was using a section of the dash to test the ground. When I tested for #1 and 2 I used a ground that I have on the firewall.

When I tested the voltage at the injector terminal there was no injector present. If I did how would the voltage be changed by the injector being there unless I put the + probe after the injector in which case it would only tell me voltage if the injector fired right?

 

btw the battery is in the spare tire well now and I have it grounded to that stud that is supposed to hold the spare tire down. It isnt exactly the best ground since its not part of the frame

im not very good with electricity, It would seem to me that if there is power up at the inj. terminals during crank then wouldnt that be enough to show that the ground at the battery is good? I never understood that little strap from the negative to the fender what with that huge negative wire from the battery to the engine block normally.

Granted that little wire once made my engine not run (i had previously assumed it was just making up for a bad engine ground on the large black wire from the battery) so you may be onto something

Im thankful for any ideas you can give me.

 

and now that I think about it, moving the battery to the rear was one of the only changes I made since I ran the car with TBI

 

Rbob got it. You have a ground problem. 8.5 volts during crank is a problem. Period. At that level, the ignition module can start to not work. Who knows what it does to the ecm. Well I guess we know one thing now..

Your trying to pull 200-300 amps or more for your starter through that little ground on the back of the motor. I was curious as to why the ecm case wasn't grounded. Now I know.

You should do a search on how to remote mount a battery.

At a minimum, you need a large gnd between the battery and frame, frame and engine. Since you have a unibody, a large gnd to the body, and a large gnd from the body to the engine.
Make sure you clean the paint from all your gnd points so you get good contact.

As a quick test, put the battery back up front with the original connections.

 

funny you should mention that because I did happen to do a search on battery relocation and didnt find much allthough i did find one post where the guy specifically stated putting a large ground from the engine to the body/chassis though he gave no explanation to why.

Looks like something im going to have to try

 

A voltage drop test is where the difference in voltage is measured between two points. Such as put one lead on the engine block, the other lead on the fender, nad measure the voltage with the engine cranking. More then 1 volt (difference) and there is a problem someplace.

As an example a number of years ago a neighbor couldn't get his truck to crank over. Only a couple of years old and in good condition. He already did the starter dance and was baffled. He found that the heavy + lead at the starter had 12 volts on it, and went to 0 once the key was turned to crank.

Using 2 straight pins I placed the + lead of the voltmeter on the + battery post (top post battery), I placed the - lead of the voltmeter on the + post clamp. The voltage read 0 (good), when the key was turned to crank the voltage still read 0 (good).

I moved the - lead of the voltmeter down the cable a few inches and pierced the insulation to contact the wire. {edit: the voltage read 0 (good)}, but when the key was turned to crank the voltmeter read 12 volts (bad).

The problem was that where the cable was molded into the clamp was bad. This didn't show up until a load was placed on the cable. The starter end had to be tied to ground (solenoid & key crank position) before the problem showed up.

With some long leads the same can be done from your battery + and - posts to areas such as the starter (from + post), the engine block, fender, ECM case (from - post).

(Measure the voltage between the battery - post and the engine block during crank. This is a voltage drop test).

The greater the voltage difference, the more likely it is a problem.

RBob.

 

With the battery in the stock location the - lead (heavy) goes directly to the engine block, this provides a ground for the starter. The little wire from the - post goes to the fender provides a good local ground for front lighting. Then there is a ground strap(s) from the engine to the firewall that provides a good ground for interior accessories.

With the fenders just bolted to the frame the two separate body grounds are requred.

With the battery in the trunk and the - on the frame there is no direct connection from the battery - to the engine block, except through the engine to firewall ground straps.

When the starter engages they are dropping a lot of voltage. This is from the high current the stater draws. They may need to be replaced as the high currents tend to ruin them (I've seen them glow red from cranking).

RBob.

 

Yeah a few times now if the car gets hot from a long drive and i try to crank it it will crank real slow and not start. This is usually followed by smoke which is obviously somethign electrical burning down there.

Another thing I was wondering that may be somewhat related, if the car is cold, like on a cold day cold, and I start it the voltage on my voltimeter will drop with rpms, the higher the rpms the lower the voltage and everything gets dim. Once the car warms up it stops doing it though.

 

you do have a couple of options, though, you can run the - lead down the frame directly to the engine block, although that means running a whole new wire. The best quick test you can do is to grab a short 2 guage wire(or bigger, can't hurt) and run that strap from the engine block to somewhere on the frame, grab the K member or something that bolts to the front frame somewhere, maybe near that small strut that ties the upper inner fender well to the frame near the AC drier(expansion tank?), use one of those pointed body bolts that are self tapping, and use a good star washer. If your ground strap is good enough in the back of the car, then you should have no problems from there. Just as an FYI you should also try and run the biggest cable you can, like a 0 guage, although most stupid batt relocation kits always ship with 2 guage, which I think is too small. During heavy cranking, that can cause some voltage drop as well. Grounds are very important, so make sure they are hooked up as cleanly as possible. The bigger the better, you cant go wrong with good grounding, esp. on efi cars.