My BIL has a 97 that starts good cold but will stall when accelerating to move. Will start fine but give some black smoke. Will also stall sometimes when warm. I have set the idle up to 900, tightened the fuel lines at the fuel filter which were a little loose and leaking but it still has the stall problem. He also feels that it is lacking some of the power it used to have. Do old and deteriorated return lines cause those problems?? Aslo would slipped timing cause it?? there is not a white smoke problem so am looking for other causes. Have spent a lot of time researching the forum but haven't found anything other than idle speed as the main reason. there must be something else that causes a stall. How about the overflow valve?? New fuel filter was installed as well. Thanks.

 

How well does it restart after stalling?

The two probable causes are that it isn't getting enough fuel and that too much load is being put on the engine. If it is an auto and the torque converter is real tight, it is possible for that to stall the motor. This is the only load related thing that I think is probable.

As for fuel, the options are not enough fuel pressure, air in the lines, and the shutdown solenoid. I haven't dealt with a low fuel pressure issue on the 12V's so I don't know exactly what the symptoms are but I would think that it is unlikely to be a LP problem since it happens under no load but could be an overflow valve problem. I also kind of doubt that there is an air leak problem since you say the truck starts well. The easiest way to check for the shutdown solenoid would be to leave the key in the on position next time it happens and look at the position of the solenoid. If it is pulled up still, that isn't the problem but if it is down, then there is something wrong with it.

 

When was the last time you changed the fuel filter.

 

Poor fuel pressure is the other cause.
A 94 with the original lift pump...probably bad by now. You need to do a pressure check.

 

It's his brother-in-laws '97

 

Change the pre-filter and fuel filter if it has been awhile. That helped mine considerably with a stall condition.

Past that, I also believe it is a fuel issue, you need to find a pressure gauge and check it.

 

Thanks guys, I believe it is a fuel issue as well, just trying to fiqure out which one. Will be looking at the pre filter and checking the fuel pressure next.