Possible ignition module problem

[aficio]

1987 7.4 tbi. All, my truck broke down on my daughter and but i was able to limp it home by driving it for a mile or so then it would die. let it cool and do it again. the ignition module was gone. I replace the module but now it acts like it is not getting enough fuel, when i first start it cold it seems okay but it warms real quick then if i try to press the gas down anymore that an idle while driving it acts like it is not getting enough fuel. If i kick it it just gets loud but does not react. I was wondering if it is possible that the new module went bad at the points for the hall effect sensor. Any thoughts.
Thanks

[Desert1957]

My 87 had similar symptoms, turned out to be a weak fuel pump. Had enough pressure for idling (barely) but lacked any throttle response.

Its in the tank if you go in search of.

Desert

[aficio]

Those were changed out last year, both sides with a new valve. This started right after i installed the new ignition module and test drove it. It has been running great until the module died.
I read where someone had broken a vacuum line and it acted like my problem and since i had to go over the engine to put the module in i checked all of those and also used a mirror to check areas that i could not easily see.

[Desert1957]

Check the two wires for the "Pickup Coil" it located inside the distributor. distributor shaft goes through the center of it, Sometimes the wires will break right where the go into the body of the coil. other end plugs into the module , They are notorious for drive ability issues.



Desert

[aficio]

Okay i put in another ignition module, i have also checked the Map sensor and just tested the truck with the map and EGR disconnected. I still have the same problem. I did not test the pickup wires since i can only check continuity. The problem seems like fuel starvation. i am thinking about changing the fuel regulator but i cannot think of a logical reason to do so and in why it would be causing the problem since i did not have the problem until i changed out the bad ignition module.

[rfmaster]

Originally Posted by aficio

Okay i put in another ignition module, i have also checked the Map sensor and just tested the truck with the map and EGR disconnected. I still have the same problem. I did not test the pickup wires since i can only check continuity. The problem seems like fuel starvation. i am thinking about changing the fuel regulator but i cannot think of a logical reason to do so and in why it would be causing the problem since i did not have the problem until i changed out the bad ignition module.

Fuel pump may have been replaced, but whoever replaced FP used fuel immersion rated hose (SAE 30R10) between fuel pump outlet and feed through? Regular hose fuel hose softens if submersed in fuel. Get a fuel pressure gauge and verify that you have 9 to 12 PSI at all times.

A bad ignition module or flaky reluctor coil may appear as fuel starvation since ECM must have DRP pulse from dizzy to fire injectors. No DRP, no injectors firing -> looks like fuel starvation.

//RF

[motornut]

my 87 when it quit, i replaced the pump,quit again realized it was power issues
found a cut on the wire over the rear wheel,green and hard baked

you could try pouring gas in the TBI,when it quits
see if it runs

[aficio]

The truck does not die, and starts up fine it is when i am driving down the road it act like it does not get enough fuel, tested the fuel pressure today and have a constant 13 psi. I guess i am about to the point of pulling the distributor and checking the pickup. The only other thing i have done, was to replace the injector pig tails, only because years ago i had a small fire and melted them, i notice the new pig tails have a cheap way they connect to the injector post, has anyone experienced drive ability problems after changing those, maybe because the connection does not carry the load as good as it needs to?

[aficio]

Okay today i installed a new pickup coil just to find out i have the same problem.
It just seems like it is not getting fuel except
at a idle or low Rpm. Can the fuel regulator go bad to where it restricts the fuel enough to create this problem?
Thanks

[rfmaster]

Originally Posted by aficio

Okay today i installed a new pickup coil just to find out i have the same problem.
It just seems like it is not getting fuel except
at a idle or low Rpm. Can the fuel regulator go bad to where it restricts the fuel enough to create this problem?
Thanks

Unlikely, FPR is a very simple device - spring loaded membrane. If it delivers 13 PSI at idle it must maintain fuel pressure at higher RPM as well. What it does point to is a low or insufficient fuel volume. At idle fuel volume requirement is relatively small - engine is not making any power, just enough to over come internal friction and drive external accessories. Fuel injectors pulses are rather short and spaced apart. Typical injector pulse width at idle ~1.2 to 1.5 mSec, injectors alternatively firing, on every other cylinder firing. As load, engine RPM increases injector pulse width duration increases and there are more injector firings. Got to have both fuel volume and pressure for injectors to supply enough fuel to meet engine requirements.

So let me understand this when you increase engine RPM above certain RPM point it begins to cut out ???

//RF

[aficio]

1987 7.4 tbi. All, my truck broke down on my daughter and but i was able to limp it home by driving it for a mile or so then it would die. let it cool and do it again. the ignition module was gone. I replace the module but now it acts like it is not getting enough fuel, when i first start it cold it seems okay but it warms real quick then if i try to press the gas down anymore that an idle while driving it acts like it is not getting enough fuel. If i kick it it just gets loud but does not react. I was wondering if it is possible that the new module went bad at the points for the hall effect sensor. Any thoughts.
Both fuel pumps and screens were changed out last year by me, both sides with a new valve. This started right after i installed the new ignition module and test drove it. IT HAS BEEN RUNNING GREAT UNTIL THE MODULE DIED.
I read where someone had broken a vacuum line and it acted like my problem and since i had to go over the engine to put the module in i checked all of those and also used a mirror to check areas that i could not easily see.
Okay i put in another ignition module, i have also checked the Map sensor and just tested the truck with the map and EGR disconnected. I still have the same problem. I did not test the pickup wires since i can only check continuity. The problem seems like fuel starvation. i am thinking about changing the fuel regulator but i cannot think of a logical reason to do so and in why it would be causing the problem since I DID NOT HAVE THE PROBLEM UNTIL I CHANGED OUT THE BAD IGNITION MODULE.
The truck does not die, and starts up fine it is when i am driving down the road it act like it does not get enough fuel, tested the fuel pressure today and have a constant 13 psi. I guess i am about to the point of pulling the distributor and checking the pickup. The only other thing i have done, was to replace the injector pig tails, Okay today i installed a new pickup coil just to find out i have the same problem.
It just seems like it is not getting fuel except at a idle or low Rpm. Can the fuel regulator go bad to where it restricts the fuel enough to create this problem?
When you press the accelerator it does not miss or die it just does not pickup speed or rpm.

[rfmaster]

"When you press the accelerator it does not miss or die it just does not pickup speed or rpm. "

1) Check and see if there any codes stored in ECM. Jumper pins A & B of ALDL turn ignition to run position, but do not start engine. You should see SES light blink code 12 12 12 pause XX XX XX pause YY YY YY, where XX, YY are codes. If there are no codes detected ECM should only blink 3x Code 12. Do not forget to remove jumper between pins A & B of the ALDL plug.

Lets do this first before anything else.

//RF

[mMad Dawg]

Have you checked the fuel filter? If its starting to plug up it will starve for fuel. Good luck.

[aficio]

Fuel filter was changed first even though the other one had less than 1k on it.
there are not DTC codes, all I
have are 12"s.
thinking about pulling the top off of the TBI and look for a restriction to incoming fuel.

[mMad Dawg]

Dont want to be a smart a55,but is the arrow on the filter facing the front?

[aficio]

No arrow, but the crimped end is forward on the filter. But thanks

[aficio]

This all started with changing the ignition module. I have not heard of it happening but I did not disconnect the battery when I replaced the module. Is there any trickle voltage there that could have damaged the ECU when I connected the new ignition module?

[homemade87]

Did you get the replacement module from the same place. Are you sure you got the correct one to begin with. There are diffrences in the modules. If you got the same module the second time there would be no diffrence in your symtom. I would do some research and be sure you got the proper module for your application. You have checked most all that would cause your problem. May be time to look at the thinks that have been changed. ( module)

Just a thought since we are chasing a ghost.


Note, I had one just shut off one time and changed it on the side of the road and did not dissconect the battery. No problems

[aficio]

Changed the ignition module with a new one from a different parts store. No difference! I was able to make it bog by just revving the engine and once i got it high enough it would just bog down and the rpm would not go any higher. I could see both injectors pumping fuel down both sides. I do not think i have ever spent this long trying to solve a engine problem.

[aficio]

I read on a different site about checking that the hose going from the tbi base plate to the PCV valve isn't cracked or broken. I also need to check for a possible restriction in the exhaust. I have not clue how this could have happened from just changing the ignition module but i will keep checking until it is right again.

[Sodell]

You may know this, but you need to unhook the battery or the ECM fuse for a while to reset the ECU after changing some parts. It sounds like it could be in limp mode. My 88, I have to unhook the battery and have it cool all the way down before I hook the battery back up. I usually leave it unhooked over night.

I would also check for codes as Mfmaster suggested.

[homemade87]

May be time to throw a timing light on it to be sure nothing has happened. The distributor may have moved or the gear on the end may have moved from a pin sheared or timing chain. Timing light should fine these problems if any. A compression test would not hurt either. Would not hurt to check at this point. Does not sound like a fuel problem if you have a good healthy flow of fuel coming from the injectors. You should have a good cone shaped fuel pattern. Not a lazy drip look. I am begining to think your module was not the problem to begin with. All the module I have ever seen go bad is either they worked or they did not. Just a coincidence it happen to start back when you changed the module .

Just a thought. Good luck

Let us know if you figure it out.

[aficio]

The truck has only 72k on it. and only gets driven about 1,500 miles a year if that. I checked for any cracked hoses and really on this truck the hoses are only a few inches long. they are replaced by metal and a type of plastic tube. but i was not able to find any cracks or breaks. I did pull the battery cable last night and connected it tonight i will test tomorrow and see what happens. I hope that for some reason it was stuck in limp mode and that is causing my problem.

[aficio]

Well tonight someone mentioned that if i was able to get it to bog down while in park, that if when i had it bogged down that if i sprayed extra fuel into the TBI that if the RPM came up then I have a fuel problem if not it is a ignition problem.
Well i was able to get the motor to bog down while in park and when i sprayed the TBI with extra fuel the RPM did nothing and the motor stayed bogged down.
can a map sensor test good electrically with a vacuum pump and a meter but still be bad in actual use.