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Cucv has bad surging issues

Hooty86

New member
7
12
3
Location
Cedar City UT
I started a thread a few weeks ago in the wrong section. Thank you to anyone who answered me there.

I have checked my transmission fluid, it is up. Since this started we have ran two full tanks of gas through the truck. Here is what I found and now I have questions.

I bypassed the fuel filter no change. I put a clear tube on the injection pump sometimes when it surges, you see air bubbles, sometimes you don't. The truck runs around town perfectly fine 80 precent of the time. It always runs down the highway fine, no smoke, good acceleration. The issue is always at idle or with no load, ie coasting up to a stop sign.
The truck always screams to the moon at start up and surges til it calms down, until you touch accelerator to give it fuel and then it revs back up. There is no smoke at idle when it is idling normally, but when it is throwing a fit it smokes blue and white. For those that didn't read my initial post this randomly started after rotating tires and have it up on jacks. This is a daily driven truck for the last three years, approximately 30,000 miles. I took the return line off the check valve thats supposed to have a little glass ball to see if it was plugged, there was no little glass ball and it wasn't plugged or any dirt or anything. We never removed the little glass ball. So today I finally decided to pinch the return while truck was running to see if it made a difference and low and behold it does. If I pinch it just right the surging goes away, and if I pinch it off closed and start it, it doesn't Rev to the moon anymore. So my question to you guys is, has anyone had their check ball break and have it cause crazy idling? If so I will buy a check valve for it, as they aren't cheap I'm asking first.

We haven't removed the check ball. This truck has been driven daily the past three years in all sorts of conditions, from 30 below to 100, no issues. Is it possible my check valve broke and caused this sudden crazy idling issue?
 

Keith_J

Well-known member
3,657
1,313
113
Location
Schertz TX
Sounds like a sticking metering valve. Idle speed is governed as well as top speed. The idle speed spring is very soft and this spring opens the metering valve. The valve is closed by the governor centrifugal force.

With key on, engine off, there is no governor force and the idle spring is fully compressed which can force the metering valve in an opened position.

Likewise, if you release the accelerator at say 45 MPH, the governor force can close the metering valve fully shut and the engine will die unless you floor the pedal.

You probably have a failed flex ring which can cause these problems.

Find the ID tag of the IP, driver side. Starts with DB2829-nnnn. The calibration number is nnnn, if you post this, I can determine if it is a flex ring pump. 4520 and 4521 are the newer non flex ring pumps from 1986. Sometime in 1985 was the switch.
 

Guyfang

Moderator
Staff member
Moderator
15,885
22,140
113
Location
Burgkunstadt, Germany
I started a thread a few weeks ago in the wrong section. Thank you to anyone who answered me there.

I have checked my transmission fluid, it is up. Since this started we have ran two full tanks of gas through the truck. Here is what I found and now I have questions.

I bypassed the fuel filter no change. I put a clear tube on the injection pump sometimes when it surges, you see air bubbles, sometimes you don't. The truck runs around town perfectly fine 80 precent of the time. It always runs down the highway fine, no smoke, good acceleration. The issue is always at idle or with no load, ie coasting up to a stop sign.
The truck always screams to the moon at start up and surges til it calms down, until you touch accelerator to give it fuel and then it revs back up. There is no smoke at idle when it is idling normally, but when it is throwing a fit it smokes blue and white. For those that didn't read my initial post this randomly started after rotating tires and have it up on jacks. This is a daily driven truck for the last three years, approximately 30,000 miles. I took the return line off the check valve thats supposed to have a little glass ball to see if it was plugged, there was no little glass ball and it wasn't plugged or any dirt or anything. We never removed the little glass ball. So today I finally decided to pinch the return while truck was running to see if it made a difference and low and behold it does. If I pinch it just right the surging goes away, and if I pinch it off closed and start it, it doesn't Rev to the moon anymore. So my question to you guys is, has anyone had their check ball break and have it cause crazy idling? If so I will buy a check valve for it, as they aren't cheap I'm asking first.

We haven't removed the check ball. This truck has been driven daily the past three years in all sorts of conditions, from 30 below to 100, no issues. Is it possible my check valve broke and caused this sudden crazy idling issue?
Do you want to keep the other thread? Or delete it?
 

Hooty86

New member
7
12
3
Location
Cedar City UT
Please delete the one in the rally section. Also I forgot to mention that at the same time my issue happened my transmission shifts at much higher rpm now like I turned up the vacuum screw in the vacuum can on Trans. Also if I turn up the base idle I can make the surging at idle way less. The truck also idles way up when I hit brakes hard. It's just a weird deal
 

ssdvc

Well-known member
971
639
93
Location
CT
Would have loved to see some in progress pics. I may have to tackle that valve myself. Was the job fairly easy and straight forward?
 
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