slow throttle response and stalls when return to idle

[Jdog87]

I bought this truck a couple weeks ago, and it drove fine when i boight it. It now will idle great and starts great, but when I step on the fuel it is sluggish to accelerate but when I release it stalls out. I'm hoping its not my injector pump but if it is it is. I jave replaced fuel filter, glow plugs, and lifter pump

 

[mblaney]

I would check for fuel flow, air, and pressure at the top of the filter. There is a schrader fitting, press that and see if you get good flow (let it run a bit, not just a squirt). Do you have an ATV tire pressure gauge? Use a low pressure tire gauge to check the same schrader fitting for pressure... should have 5 psi or more. These two tests will quickly tell you if you have a supply (lift pump) problem. Just because you installed a new one does not mean that it is working, or that it was installed correctly.

After that, can you IP check timing? When cold do you have a noisier diesel rattle that quiets down once the cold advance comes off? This would indicate that you are 'close enough' that it should drive ok.

Since it drove well until you changed the lift pump I suspect you have a supply problem. Why did you change the lift pump (I don't need to know, you must have had a reason though)?

Glow plugs have nothing to do with it once the engine is running. You start well so you can eliminate that.

P.S. If you ever need to change your lift pump I would always recommend installing an electric. Well worth the effort!

 

[mblaney]

And welcome to Oilburners!

 

[Jdog87]

to install a electric lift pump do i have to delete the manual one. The reason I installed a new lift pump was because it was running terrable. The lifter pump was cheap and felt like it was the problem. I will check the shrader valve for pressure.

 

[Jdog87]

Oh and thankyou for your help and the welcome.

 

[Jdog87]

Lifter pump is working good. I'm getting about 6 psi. Throttle response is decent but it still stalls out when i release the throttle.

 

[79jasper]

90% of the time, those symptoms end up being a bad ip. Sometimes you can do "the ATF trick," or similar. Personally I would use a real diesel treatment.

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[hadley000]

still stalls out when i release the throttle

I had the same problem with stalling after letting off the pedal for a while and it turned out to be air intrusion. Mine started fine too. When you press the schrader valve does air come out?

But, it wasn't sluggish though.

 

[Jdog87]

I didn't see much air if any . I know i had a couple injectors that were wet and i was going to replace the o rings in them.

 

[Thewespaul]

Get those leaks squared away and make sure you have a full tank of diesel. New fuel filter and fill with atf when you install it, should narrow it down to ip if it continues

 

[gandalf]

Most of your symptoms sound like the IP, more specifically the metering valve in the IP. It sounds as though that metering valve is sticking.

I'm a firm believer in trying the easiest and least expensive fixes first. People have mentioned running ATF through the system. That has worked for many of us, myself included. Fill the fuel filter with ATF and install it full. Then start the truck, and as soon as it sounds a bit "different" shut it down. That may take anywhere 15 to 30 seconds. Let the truck sit overnight that way. The next day start it up and drive, drive like you stole it. Do that for just a little while. Frequently that's all you need do to fix the sticking metering valve.

Always add a diesel conditioner to the tank(s) every time you fill them. Out trucks like more lubricity than they modern diesel provides.

Report back on the results.

 

[icanfixall]

You sound like as posted.. The metering valve is sticking. Filling the filter with auto trans fluid or a fuel conditioner may clean up the injection pump.Please do not pour and fluid or fuel conditioner down the intake. That will cause the engine to probably run away because fuel going directly into the engine has no way for the injection pump to act like a governor. Our injection pumps have an internal governor that cuts back the fuel to maintain both rpm and power outputs. Bypassing it and the engine will gain rpm to the point of throwing rods.. Go to u tube for runaway vids.

 

[theSHERPA]

I had same issue. Folks here said to try the ATF trick. I did, and the problem stopped and has been clattering along ever since.


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[Macrobb]

I'D also get a cheap pressure gauge on the fuel supply(take out the fuel filter/vacuum sensor on the filter head, it's a 1/8 npt port), and put it somewhere you can see from inside the cab. I've had this issue from a partial blockage/limited air in the fuel on one truck. Replacing the IP with a known good one did nothing.

 

[Shadetreemechanic]

You don't have to delete the manual pump as long as the electric one is downstream of the manual one. They work in tandem well, but if the manual one fails and the electric one is in front of it, the electric one could pump diesel into your crankcase. As long as the electric one comes after the manual one its a non issue.