87' R10 TBI 350 shuts off when driving. HeLP

[Hunter_Michael]

**Update** - it has been two days since replacing the ignition distributor Pickup as recommended (had to remove distributor & take apart to replace, very easy to do). It has not died while driving. It could have been the pigtail from the coil to the ICM that one of the connections was hanging on by a thread as well, But really think the Pickup coil could have been the issue. If I could diagnose a random shut off again, Id start whith replacing the Pickup coil and the ICM and also check the pigtail wiring that attaches to the dizzy from the coil and see if that fixes your issue. Thanks again for all the help from eveyone. This forum have been invaluable.

**Initial Post**
I been working on this new to me 1987 Chevy R10 TBI w/ a 350ci & a 700r4 tranny dual fuel tanks. Here are the things I've replaced but still cuts out randomly when driving like the fuel pump shuts completely off until you pull over re cycle the key and it starts right back up like nothing wrong..

Replaced coil & spark plugs
Inspected cap, rotor & plug wires
Replaced fuel filte
Replaced MAP Sensor & throttle posn sensor on TBI
Replaced idle air control valve on TBI
Replaced Ignition control module on distributor
Replaced coolant temp sensor on manifold next to water neck.
Replaced gasket on water neck fixed leak.
Replaced thermastat
Replaced egr
Replaced passenger side fuel tank along w/fuel sending and pump etc. New hoses
Replaced fuel tank switch and fuel tank selector valve
Replaced oil pressure sending unit wire
Replaced water temp wire
Replaced oil sending sensor on manifold and plug
Rebuilt TBI
Replaced knock sensor and wire
Ignition control module
Ignition switch.

The truck runs great just has this random shut off while driving. Nothing really could cause it except maybe heat? No bumps in the road that could jiggle a gound or somwthing and the oil pressure is alway 30psi or higher.

 

[Ricko1966]

How much fuel is in it when this happens? Will it happen with a full tank? Doesn't sound like heat to me. The hot part doesn't cool in the 10 seconds it takes to cycle the key. Make a long test light,mine is a piece of speaker wire an an LED. Backprobe the lead at the coil ,connect 1 lead of speaker wire,ground the other one. Tape the end with the LED to the windshield. Does the LED go out when it dies? P.S. LEDs are polarity sensitive,so mine is actually 2 LEDs flipped so no matter how you are connected 1 LED is getting correct polarity.

 

[gmbellew]

does it ever throw a code? are any codes stored?

 

[SquareRoot]

LS swap

 

[Hunter_Michael]

How much fuel is in it when this happens? Will it happen with a full tank? Doesn't sound like heat to me. The hot part doesn't cool in the 10 seconds it takes to cycle the key. Make a long test light,mine is a piece of speaker wire an an LED. Backprobe the lead at the coil ,connect 1 lead of speaker wire,ground the other one. Tape the end with the LED to the windshield. Does the LED go out when it dies? P.S. LEDs are polarity sensitive,so mine is actually 2 LEDs flipped so no matter how you are connected 1 LED is getting correct polarity.

Ricko ~ I will add this & let you know. What would the light going out signal? Also is there a way to bypass all the safety shut off stuff? I know the oil switch controls the fuel pump to shut off if it goes below 3psi or something like that. Id like to bypass that to see if thats the issue. the pressure never does go below....
I dont ever get a code after which is weird. My son had it happen again this morning while driving to school, a little over 1/4 tank fuel. Ill re-check and see if a code popped once he get home from football practice.

My Next check will be the ECM. An LS Swap may be in the future, but would really like to get the origial 350 runing properly, as it would be cheaper at this point.

Thanks everyone for your input and help.

 

[Ricko1966]

If the light goes out you lost power to the coil.keep your tank 3/4 or above for awhile, see if that makes the problem go away.

 

[gmbellew]

The oil pressure switch doesn't turn off the fuel pump if the pressure gets low. But it does serve as a backup to the fuel pump relay to send power to the fuel pump once the pressure gets to 2 or 3 psi from extended cranking or allows you to keep driving if the engine is already running. That way you aren't dead in the water if the relay goes out.

 

[Hunter_Michael]

The oil pressure switch doesn't turn off the fuel pump if the pressure gets low. But it does serve as a backup to the fuel pump relay to send power to the fuel pump once the pressure gets to 2 or 3 psi from extended cranking or allows you to keep driving if the engine is already running. That way you aren't dead in the water if the relay goes out.

Gotcha, I got wrong info from a mechanic friend that said 87' tbi had a low oil safety that would shut the fuel pump off. The shut off of the engine while driving only happens when driving, not while idling... This is so random its frustrating...

Ive seen other posts of the same issue with the 87 randomly dying while driving but no one has posted their fix. Weird this one year vehicle is so problematic.

 

[gmbellew]

I've had shutoff issues on my 90, for a variety of causes. Usually I have a code or a fuse blown to help diagnose. Often a blown fuse is from a short to ground somewhere in a critical ECM circuit (ECMB or ECMI). I've had bad plug wires arcing to ICM wires causing this issue, usually it will sometimes throw a code 42 also. I've had a bad ICM, but usually it doesn't restart until it has been swapped.

 

[Ricko1966]

The reason. I'm telling you see if the problem goes away with a mostly full tank,is if the pump pickup comes uncovered on a TBI car they will die,right now,but start right back up. I'm just trying to rule out the pump pickup coming off,a tank baffle broken loose,or the wrong tank installed.

 

[Hunter_Michael]

I checked for a code after my son came home from school and no codes...Im going to add that led light and see if it looses power to the coil.

 

[gmbellew]

I checked for a code after my son came home from school and no codes...Im going to add that led light and see if it looses power to the coil.

did it at least flash 12 so you know the SES light is working?

 

[Hunter_Michael]

did it at least flash 12 so you know the SES light is working?

It did the 12 yes

 

[F-64]

Does anything else electrical act strangely? Does your radio cut out? Voltage gauge needle not steady? Lights flicker? Does it only happen when hot? After how many minutes after startup does it begin to act up?

 

[JamesSam]

Following this thread as my 87 has acted like it might cut out when leaving from a stop before. After this happened the first time I decided to put in all new plugs and wires. This seemed to give it new life. Recently it happened again while out driving. I also had the drivers side tank die and kill power to the truck about a year ago. Now only running on passenger side. Lots of strange nuances, but bottom line: I know the truck could benefit from new tank, lines, and sending units. I know I should also probably exchange ignition coil and see about cleaning the throttle body injectors etc. Watching for info now....