[greengurugear]

Recently our 1991 350 ambulance has been suffering some odd behavior. A few weeks ago it started to stall out after going up steep hills (in CO) after removing ones' foot from the acceleration pedal. It would then take a bunch of pedal pumps (usually never needs any to start cold) to start back up only staying running with the fuel pedal pressed slightly. If ones foot is taken off the pedal it will rough idle and then stall out. Then it takes a bunch of pumps to start again and the only way to drive it is to keep one foot on the fuel always pressed down slightly then use the other foot to brake, making sure not to take the foot off the fuel and have it stall out (very scary in a heavy ambulance in the mountains).

Taking into the fact the ambulance has been converted to run on SVO and likes biodiesel too, it seemed time to change the filters.

Once the filters were changed on both sides of the system, no luck, same problem.

Then we figured it might be the the lift pump. After doing some tests it seemed as if the lift pump was not functioning fully so it was painstakingly and carefully replaced with a NAPA one. After the ordeal, it cranked pretty much right up. Bleed air from the fuel line going into the injection pump and we seemed good to go. Drove it around for a few days with now problems and it cranked right up every time cool and warm.


Then it was down the mountain where it acted fine, was good all round town, then it just stalled out after comming up 15 miles of a steep road when I took my foot of the fuel pedal to apply the brake.

Apparently it wasn't the lift pump.
What is going on?

I had also ajusted the idle but that didn't seem to help as it still cuts out after a hard throttle and then removing the pressure from the fuel pedal.

We are suppose to leave for a big trip tomorrow and would hate to take the gas guzzler. Any body have any ideas?

Thanks.

 

[OkieGringo]

Stalls returning to idle after snapping throttle open. Injection pump problem caused by poor quality or contaminated fuel. Check for presence of water in the fuel--removal of the injection pump governor cover may be necessary to find contamination, but is not advisable unless you have experience. Check idle speed setting and injection pump timing, as well as cold timing advance--timing should advance at least 2 degrees with 12 volts applied to the rear solenoid terminal. Adding Stanadyne's All Season Diesel Fuel Conditioner may cure this problem, but if it persists, or if there is no cold advance, replace the injection pump. Recommend that the Stanadyne All Season Fuel Conditioner be used periodically to prolong injection pump life.

 

[cdnsarguy]

Could be the IP inlet filter is plugged..... or as Okie said grunge in the IP... sent you a PM.

 

[bucholzi]

[ QUOTE ]
Could be the IP inlet filter is plugged..... or as Okie said grunge in the IP... sent you a PM.

[/ QUOTE ]

I have a similar problem (cuts when I go off throttle), so if you have info about possible fix, please pm it to me too.

 

[94_turbo]

or--the governor ring in the ip could be breaking up---older gm diesels would do that when the ring started to break

 

[cdnsarguy]

To check for governor ring disintegration, remove the 90* filtting from the top of the IP and see if there are black specsjammed in the check valve......or catch IP return fuel from IP in a clean white container and look for black specs. Most rebuilt IPs do not have that old ring anymore.

 

[94_turbo]

MOST being the key word----- /ubbthreads/images/graemlins/biggrin.gif /ubbthreads/images/graemlins/biggrin.gif

 

[350 long rod]

I had the same problem.It was the throttle valve inside the IP.You have to take the top off the IP and remove the linkage to get to the valve.I was able to tell that there was a problem with it because if you tried to move it from the closed position it was a little sticky.When you let of the gas it slams the valve to the closed position and cannot get it back open soon enough and the engine dies.Mine would restart fine sometimes you could just let the clutch back out and restart.To clean mine I pulled the vavle out and sprayed carb claener in the bore had lunch then sucked the cleaner back out with a hand vac pump.Put some bio diesel in the bore and put the valve back in it was much easier to move then.DO NOT do any thing to the valve besides cleaning it with carb cleaner and lubing it with diesel.I tried running a straight shot of Stanendyne fuel additive filled the filter with it but that did not help any. Hope thgis helps I think mine was from veggi,IE not getting a good purge and not having a return bypass for purge both fixed now.

 

[agnem]

That thing your talking about is called the metering valve. Somewhat difficult to service because you have to remove the guide stud, and when you do that, you loose some adjustments that are calibrated by the pump rebuilder. That's not to say you can't do it, because whatever those adjustments are (which I have been told have something to do with the ride height of the metering valve) they don't seem too critical. Beware of the spring that lives inside the guide stud. You don't want to drop any parts inside the pump, if your working on it in the truck.

 

[350 long rod]

Yes your right on the valve I was to lazy to dig out my manual and it was late.Any one taking apart a IP better have a good strong mechanical ability mine is much better than my spelling ability.I forget that alot of people on here to do not have that but I will post what has worked for me next time I will add a warning.I marked the threads on that stud so I could get it back together the same way there again a normal thing for me when taking apart some thing that I can see has a specific adjustment.

 

[90Ford73]

Question

To check for governor ring disintegration, remove the 90* filtting from the top of the IP and see if there are black specsjammed in the check valve......or catch IP return fuel from IP in a clean white container and look for black specs. Most rebuilt IPs do not have that old ring anymore.

Hello, I have the same problem. Do I remove the 90* fitting itself, or the nut attached to it. If not the nut, what does the nut do? Thanks

 

[Bill1013]

That's a really old thread. But here is what cdnsarguy is referring to. The "nut" is the check valve itself.

 

[90Ford73]

That's a really old thread. But here is what cdnsarguy is referring to. The "nut" is the check valve itself.

Thanks a lot Bill1013, those pictures help!! So in order to remove the 90* fitting, I have to remove the nut right, as it is all one piece? Nothing will move inside the pump if I do this, as I don't want to take the pump apart

 

[90Ford73]

Thanks a lot Bill1013, those pictures help!! So in order to remove the 90* fitting, I have to remove the nut right, as it is all one piece? Nothing will move inside the pump if I do this, as I don't want to take the pump apart

Stupid question, I see now. I will take this apart when I get time. Thanks again!