Engine/Transmission (1994 - 1998) engine idle....overflow valve?

[DPashko]

i recently bought a 97 auto truck with 300 000km, it is stock except I put in a 100 plate. It wanted to stall when the AC was on. I adjusted the idle and was fine for a few weeks. Now when the truck has sat overnight you start the truck it idles about 6-700rpm until engine warms up then its back in the 850 range... AC off. But today after a long trip, AC was off when i came to a stop the truck wanted to idle in the 6-700 rpm range when in gear. If you blip the throttle it will almost want to stall. . , but in nutural it would go back to about 800rpm. Could this be the overflow valve?



I will try it again tomorrow morning and see what the idle does... cold and hot. Probably re adjust idle.

 

[Missouri Mule]

By doing a fule pressure test you can check out the overflow valve. When doing the fuel pressure test take a pliers and squeeze the return fuel line if the pressure goes up its the overlow valve if pressure stays the the same or goes up very slow it is the lift pump.

You can also take the overflow valve out and check the length of the spring(should be . 50 inch). You will have to file the bolt down some to get it out while p7100 pump is on truck, also stick cloth between block and pump to catch anything that falls out/down.

 

[Joseph Donnelly]

TST offers an adapter that screws into the bleeder screw position on the fuel filter. If you remove the M8 holddown bolt (10 mm head)near the middle of the pump on the engine side (the fuel return line has a strap under the bolt head), and remove the little M6 screw at the very rear of the pump (8 mm head), you can swing the return line and remove the overflow valve and its banjo bolt without a problem. You probably should replace the fuel return hose anyway. You can increase the idle speed a bit (the adjusting bolt is at the rear of the pump) and see if the situation gets better. If someone put in governor springs incorrectly, or tightened the governor spring adjuster nuts too much, the engine will have trouble idling.

 

[DPashko]

I checked the over flow spring it was 0. 46". I strecthed the spring out slightly to 0. 51 to see if it would make a diference. There was no difference in idle. I re-adjusted idle and took it for a drive, and everything seemed fine. I will just wait and see if idle changes again after some driving is done. the lift pump is fairly new, screen is clean, and fuel filter is new.

Im wondering if the throttle cable is stretching a bit... an older fella owned the truck before and probably never worked the throttle as much as I do... . hahaha