(jump) starts fine but stalls when I shift

[89/90]

I've been rebuilding my 89/90 for a while now, and had finally gotten it running again. It's become mostly a farm truck at this point, so I didnt really care that the battery is an old one I had laying around and doesn't hold a charge for more than a day. But the problem started when I pulled up to my driveway, and as soon as I put it into reverse to back in, it the motor stalled. Since the battery is junk, I had to then jump it again, only to have it stall again when I put it in reverse again. Now, it's worse and I can't even put it in drive or any gear without it stalling.

Any chance this is just a battery and/or alternator problem, or could it be something more- like a torque converter or something in the trans?

It's a 350 w/ a 700R4

 

[84 k5 blazer]

So the motor runs fine until you put it in gear then dies. Sounds like the TQ is locked which would cause the motor to stall.

 

[89/90]

Yeah, motor runs just fine, and as soon as I pull the gearshift down into any gear it instantly dies...and not like a bogg/sputter down, it cuts off right away. Happens if I rev it up a little before shifting too.

 

[Fordum]

Leave the jumpers in place, crank it, put the brake on and see if it will keep running when you put it in gear.
Having the jumpers hooked up should eliminate any power problem.
I suspect that it will quit with the jumper hooked up too.

If so, then its most likely transmission related. Probably the torque converter.

 

[scrappyk5]

Leave the jumpers in place, crank it, put the brake on and see if it will keep running when you put it in gear.
Having the jumpers hooked up should eliminate any power problem.
I suspect that it will quit with the jumper hooked up too.

If so, then its most likely transmission related. Probably the torque converter.

ditto on this reply. if you keep the cables on it and your able to now shift and move, then its because the battery is soo far gone, any current draw will kill the truck. But if it still dies, then most likely the t/c.

 

[diesel4me]

Sounds like the battery is so dead it cant power up the computer fully,or the fuel pump--newer EFI vehicles need much more juice available that old HEI or points equipped trucks did....

I had a bad distributor rotor one day that caused my engine to die when I'd put it in gear,and it was near impossible to get the truck to move without stalling ,you had to feather the gas and it was backfiring and cutting out....once I discovered the rotor had a burnt spot in its center that was letting spark ground out there and I replaced it,the truck drove fine again..it was weird,in neutral or park it ran perfectly but it'd stall as soon as I put it in reverse or drive with the bad rotor..

It is possible its the torque converter not unlocking too,unplugging the wire going to the tranny will tell if thats the cause,but I'd test it with a full 12V from a good battery or jumped to another vehicle first,its probably just low violtage..

 

[ryoken]

yup, my dollar is on low voltage, not a driveline issue....

 

[Jessie James]

The TBI throubleshooting manual says to check voltage of the alternator (9 - 16 volts), and to check the ground which is right behind the alternator on the top of the block (this is where the ECM grounds). If your motor mounts are grounding out (trashed) that is also top of the list.

Low voltage causes the ECM of the TBI system to fail in a multitude of ways.

If I were you, I'd toss a different battery in there for a few minutes and see what happens.

 

[89/90]

i put in a good battery and it still cuts off if i shift into any gear.

 

[4X4HIGH]

I would suspect a short at the ignition switch when you shift it into gear. The shifter could be moving some of the wires around and one may have a bad spot in the insulation and ground out against the column when shifted. To check if it is the TC not disengaging you should be able to simply pull the plug on the drivers side of the trans to eleminate that as being an issue.

 

[89/90]

revised below

 

[89/90]

well i couldnt find the torque converter connector plug at first because it was already unconnected and hanging on the passenger side. in fact, the plug was completed melted together--i guess it was sitting on the exhaust at some point. anyway, i cut behind the plug in case it being melted together was causing a short, and what do you know- started it up (with a good battery) and it shifted just fine!

so i found one place to get a new connector, and another that looks like a kit for manual lockup

most of the electronics are disabled so i'm thinking of doing the manual one. anyone knows what happens if i drive without it plugged in in the mean time? (farm truck, so low speeds)

 

[diesel4me]

Driving it at highway speeds fast enough that the converter should be locked up "might" overheat it and damage it if driven far & long enough....at speeds under 35-40 mph it would be unlocked anyway,so it wont matter..

When I first bought my 81 G-10 van,its TH-350 with lockup converter wouldn't lock,unknown to me...I had to put a govenor gear on the tranny's govenor,when I first got it all it had was first gear & reverse--replacing the stripped gear fixed that,it shifted fine now into second & third,but the converter wouldn't lock up,I was unaware of that until I drove it 80 miles to my brothers house,when I got there it peuked tranny fluid out of the dipstick tube it was so hot!...he quicly determined the brake light switch was out of adjustment,and that kept the converter from locking up--adjusted it and it was fine after that,I put 40,000 miles on it after that with no issues with the tranny...

A manual switch is OK,as long as you dont mind (or FORGET) to switch it on to lock it at higher speeds,and shut it off at stoplights so it wont stall!..I'd say fix the stock setup,its a lot easier to drive without having to fool with switches..