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Discussion Starter · #1 ·
Well I went through the usual diagnostic tests but I’m stuck on this one. 87 reliant 2.2 TBI automatic. I’ve been daily driving this for work the last couple months because of diesel prices, so I don’t want to drive the truck back and forth at $6.50 a gallon. Left for work last night and made it only 2 blocks from the house before it stalled at the stop sign. No time to mess with it, so I walked back home jumped in the truck and went to work.

Earlier today I went back down with some tools and started messing with it. Fuel pump primes, it’ll fire for a second, then stalls. Will not fire again unless you let it sit a while.

I pulled the regulator and there’s fuel there. Briefly cycled the key and it’s pumping fuel no problem. Ohm’d the injector coil and it’s 1.4-1.5 ohms. Jumped 12 voltsdirect to the coil and it clicks and you can see it spray down the throttle body. Then probed the injector connector and cranked it. It was bouncing around (as I would expect it to since I would imagine it runs a PWM signal) but was in the neighborhood of 1.5-2 volts. Car will start on ether and continue to run if you keep feeding it ether.

only thing I can think is I’m not getting an accurate reading on the voltage going to the injector using the normal DMM. Any suggestions are appreciated!
 

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If you feel it is a fuel issue you need to verify...
1)No fault codes are stored in memory.
If there are, write them down, clear the codes (battery disconnect, then be sure they cleared), then crank the engine 7-10 seconds and recheck for codes.
Are any fault codes present?

NOTE...The MAP Sensor is the Dominant fuel control sensor on the car.
The underhood mounted MAP Sensors were a high failure item on 87-91 TBI cars.
Back in the 80's we had numerous K-Cars (leased corporate vehicles) towed in with no start issues and 90% of the time the issue was the MAP Sensor, got to the point we just walked out to the car, plugged in a known good MAP Sensor and drove the car into the bay, then called the leasing company for approval, it was so common when we called they laughed and said "MAP Sensor, right?,
Look for a Fault Code 13 or 14, if no fault codes are present verify that the Barometric Pressure Reading is correct and that vacuum changes from key on to engine cranking.

2)Fuel Pressure (13-15 PSI) (Remains constant under all operating conditions)
To check fuel pressure you need an adapter with a service valve to connect to the TB and to connect your gauge)
Artifact Wood Metal Fashion accessory Nickel

You can rent a Master Fuel Pump Gauge Set at AutoZone.(Free)

3)12 volts are present at the injector while cranking the engine.
a)Power is a constant 12 volts, the engine controller controls the ground side of the injector, pulse width is determined by info received from numerous sensors (MAP, CTS, O2 (in closed loop only), ACT, TPS, etc.)
b)There will only be power present for 1 second with initial key on, there will not be power present again until the engine controller see's a crank/rpm signal from the HEP.(Hall Effect Pickup), this also holds true for power to the fuel pump and + coil.
c)If you disconnect the fuel supply (unplug the fuel pump connector) you can use a Noid Light to check Injector power/pulse.
You can rent these at AZ also.

If all of the above check OK, you may want to look at...
1)Main Engine Controller Ground is securely connected
a)On the turbo cars this ground is connected to a fuel rail mounting bolt (older models) and from the manifold (passenger side) to the firewall (on newer models), not sure where it is located on a TBI car.
2)Cam Timing is correct, belt may have jumped.
 

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Discussion Starter · #3 ·
Thanks NAJ!
I forgot to mention there were no codes present, which I found odd.

I didn’t realize how strongly the MAP was tied to fuel delivery. I mean I know it is measuring vacuum (or boost in turbo applications) and that corresponds to the fuel map,but I had assumed a failed MAP still would run the car and the LM used input from other sensors to limp it home? (Like when you do get a 13 or 14 and the car gets limited to 2000rpm. I used to have that happen on a TII Daytona years ago until I found a bad plastic tee that kept blowing off the line)

I don’t think I have a 1 bar MAP to replace this one with, could I connect a 2 bar MAP strictly to see if it would get the engine to fire up? If that worked I’d buy the proper one and get the car back home (it’s still parked in front of my neighbors house 2 blocks down the road)

Fuel I was only able to verify fuel present and SOME level of pressure as I don’t have the proper adapter (with the regulator removed and the keyed briefly cycled it began to flow. Also when it was all put back in place and I jumped power to the injector directly it gave what appeared to be a satisfying spray pattern for that second or so)

Oddly, for how well equipped my home shop is, I don’t have a noid light lol. Is my checking the voltage with a standard digital multi meter a waste of time due to the voltage being PWM? If I’m remembering correctly I was only getting 1.5-2.5 volts at initial key on and slightly less during cranking. (This was done via unplugging the injector and probing both pins directly). I suspect the DMM is not an accurate measurement due to the aforementioned issues.

HEP and coil are seeing power as the car will continue to run if you keep feeding starting fluid in the TB. Looks like I’ll be running to my buddies garage to borrow a noid light.

If those things all check out, I’ll look to the grounds.
If I disconnect the MAP electrically, wouldn’t that run in limp mode and just give me a code 14? Perhaps if the MAP failed in such a way as to be a dead short it wouldn’t fire the injector at all but unplugging would give me an open circuit instead?
Other thing possibly worth mentioning, I had been driving this car even the night before it ran well, that next morning we had some pretty hellacious rain and possibly that effected something (though I can’t realistically see water having got up into the MAP etc but you never know)

Thanks for all the help!
 

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Discussion Starter · #4 ·
So down at the car now. MAP plugged in or unplugged makes no change. Using DMM and have ground probe directly mounted to negative terminal of battery, I get a brief jump to approximately 3.xx volts at injector electrical connector during key on. Between 1.5 and 2.5 volts during cranking.
 

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I only mentioned the MAP Sensor as a possibility, without further diagnostics... you can view the voltage with your DVOM, I posted the link in post #2.
You cannot use a 2 Bar MAP in place of a 1 Bar MAP, the voltages are completely different, the TBI engine controller cannot read/decipher the turbo MAP Sensor.

As I stated, you can rent both a fuel pressure gauge and noid lights from AutoZone, they are free.
You leave a deposit which is fully returned when you return the tools.

As far as injector power...
I have not worked on an 87 or older TBI car in 30 years, I never really paid much attention to it but the wiring is throwing me for a loop.
Normally, and on every Chrysler FI system I have seen or been trained on (that I can remember) the ASD Relay provides power to the fuel injector(s), + coil, fuel pump and on later vehicles the HO2S and alternator field circuit.
The reason for this is safety, in the event of a collision where the engine stops running (without a crank/rpm signal the ASD will not be actuated) power is disconnected from the fuel and ignition system to prevent a fire.
Looking at the wiring for 84-87 TBI cars the ASD Relay is not providing a constant 12 volts directly to the injector, however, it is on the turbo cars.
The wiring to the TBI injector shows a TN and WT wire, neither of which is the ASD output wire which is DG/BK.
Looking at the pinout I have for the 85-87 PM they show cavities 5 and 7 of the 10 pin connector are both "injector control circuits" which is where my confusion is coming from, my best guess is that power is supplied on one of those wires internally through the PM but at this point this is just a guess on my part, it has been too long.
88 TBI wiring (SMEC) shows a constant 12 volts from the ASD Relay to the fuel injector, 88 is also the year the controllers changed from LM/PM to SMEC and the ASD Relay was removed from the PM and mounted underhood.
84/85 TBI cars were high pressure fuel injection, 86 they went to a low pressure system and used that until 1991 1/2, the Chrysler parts catalog shows different part #'s for the injectors between 86/87 and 88-91, the difference?
Basically, I am not entirely sure if there should be a constant 12 volts on the 86/87 TBI injector but common sense says Yes.
I do have a Chrysler Fuel Injection Principal and Theory Manual at home, I can look on Monday when I get home.
I will also reach out to another member for a refresher course.
I will send you a copy of the wiring through PM.
 

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Discussion Starter · #6 ·
Thanks so much you’ve really gone above and beyond. I was trying on google to find a schematic but couldn’t find the one I needed. I’m wondering if it’s possible that an 87 TBI car might be switching the 12volt signal for injector actuation as opposed to ground, though it would seem weird that would be contrary to the rest of them
 

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I just sent a PM to a very knowledgeable member who hopefully has a better memory than me, (I was trained on these cars in 1986) waiting for a reply.
I also sent him a link to your thread so he may respond in your thread.
 

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I did receive a reply.
He is in the same position as me, never really paid attention to the power supply to the 84-87 TBI injector and just assumed as I did that it was supplied by the ASD Relay.
He also agrees that the injector should have a 12 volt power supply to energize the injector coil.
I will check my Principal and Theory manual tomorrow.
 

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Well I went through the usual diagnostic tests but I’m stuck on this one. 87 reliant 2.2 TBI automatic. I’ve been daily driving this for work the last couple months because of diesel prices, so I don’t want to drive the truck back and forth at $6.50 a gallon. Left for work last night and made it only 2 blocks from the house before it stalled at the stop sign. No time to mess with it, so I walked back home jumped in the truck and went to work.

Earlier today I went back down with some tools and started messing with it. Fuel pump primes, it’ll fire for a second, then stalls. Will not fire again unless you let it sit a while.

I pulled the regulator and there’s fuel there. Briefly cycled the key and it’s pumping fuel no problem. Ohm’d the injector coil and it’s 1.4-1.5 ohms. Jumped 12 voltsdirect to the coil and it clicks and you can see it spray down the throttle body. Then probed the injector connector and cranked it. It was bouncing around (as I would expect it to since I would imagine it runs a PWM signal) but was in the neighborhood of 1.5-2 volts. Car will start on ether and continue to run if you keep feeding it ether.

only thing I can think is I’m not getting an accurate reading on the voltage going to the injector using the normal DMM. Any suggestions are appreciated!
try unplugging the speed sensor I've seen it short and shut the computer down. Also verify fuel pressure...
 

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Discussion Starter · #11 ·
I did receive a reply.
He is in the same position as me, never really paid attention to the power supply to the 84-87 TBI injector and just assumed as I did that it was supplied by the ASD Relay.
He also agrees that the injector should have a 12 volt power supply to energize the injector coil.
I will check my Principal and Theory manual tomorrow.
Thanks NAJ! Warren on the other forum said the earlier TBI’s are in face constant ground and the positive is pulsed instead, not using a traditional injector driver but a similar circuit. It doesn’t solve the problem per se, but it gives an answer to one aspect so I’m not chasing my tail on that
 

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Thanks NAJ! Warren on the other forum said the earlier TBI’s are in face constant ground and the positive is pulsed instead, not using a traditional injector driver but a similar circuit. It doesn’t solve the problem per se, but it gives an answer to one aspect so I’m not chasing my tail on that
Yes, I just read that, sure I was trained on that but it was so very long ago.
Book Publication Font Plant Paper
Book Font Publication Handwriting Parallel

Chrysler has a logical diagnostic sequence for No Starts and Driveabilty without fault codes.
The best/easiest way to determine the cause of the no start is start at the beginning and work your way down until the cause of the problem is uncovered.
Font Parallel Rectangle Document Number


There are two other things that could create your starts/stalls problem.
1)Alarm System
2)TPS closed throttle voltage above 2.50 volts.
 

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Thanks NAJ! Warren on the other forum said the earlier TBI’s are in face constant ground and the positive is pulsed instead, not using a traditional injector driver but a similar circuit. It doesn’t solve the problem per se, but it gives an answer to one aspect so I’m not chasing my tail on that
When I put my 88 TBI engine together it wouldn't start because I left the O2/IAT harness unplugged the ground that was holding it back was the one on the oxygen sensor harness it's a wire that bolts to the side of the head maybe clean it or something. You can see it here in the video it's the back right corner of the head where the oxygen sensor is supposed to plug in and you can see the bolt and the ground wire....

 

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Discussion Starter · #14 ·
I know it’s been a long time since an update but I forgot to post the fix on this one.

as it turned out, the fuel pump was bad. earlier in the thread I explained that the car would start on ether and remain running if you kept feeding it more ether. Also when you’d cycle the key on you would hear the pump activate. If the ASD relay was grounded you’d get the pump running continuously as it should. Pulling a fuel line off the throttle body it would spray fuel when the pump was powered.

what I never did was measure fuel pressure! I ended up changing the injector believing that must be the issue, but to no avail. I didn’t touch the car for a while and the next time I messed with it the pump was now completely dead. Key on, ASD grounded, even jumping power directly to the pump pigtail, it was locked up solid. I ended up installing a 255 pump as it would need one for the TIII anyway (yes that’s still happening, it’s just been on the back burner for quite a while). The car fired up no problem.

moral of the story: don’t assume because the pump runs and fuel is flowing that it can’t be the issue!!
 
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