View Full Version : Rebuilt IP surge
I just put in a gear timing set from DSG and while in the area had the old DB2 4544 IP overhauled. Have noticed now the engine wants to surge when I increase the throttle from idle. It also doesnt want to keep a steady RPM while going down the road at almost any RPM
Have changed the fuel filter and bleed the system finding no air. I think there is a governor seal that may have been installed incorrectly by the rebuilder however, wanted to see if any of this surging could be the timing gear set.
Going from Idle it will jump from about 800/1000 RPM to about 1400/1600 instead of a smooth increase. On the road I hear and feel the RPM changing more than see it on the TACH.
Any thoughts appreciated
SteveMc
john8662
02-01-2005, 21:41
How long has this been happening? I noticed when I installed my new pump and DSG gears that it did this for about the first minute of running, but smoothed out soon after. Air will cause problems in these pumps, but I suspect something else in your decription, mainly beacause it still occurs after a test drive.
Another thing it could be is the lift pump, when was the last tiime that item was serviced? Is the 6.5 a newly installed engine?
John.
Yes this engine was just installed after the 6.2 broke the crank. Lift pump is new and was checked. Good pressure at filter and no bubbles. Have put 400 miles on engine and still surges but, seems to be a little better or else I am getting used to it.
jonflies
02-18-2005, 18:33
How are things going now? I would still look for an air leak on the vacuum side of the pump.
More Power
02-18-2005, 20:28
Something to consider.....
The Banks 6.2TD I owned would also surge if: 1- The HPCA was energized and 2- If the fuel filter needed to be changed.
I theorized at the time that a 6.2 DB2 pump that had been "turned up" became a little more fussy about fuel supply pressure, especially when the cold advance was energized (lower housing pressure).
MP
britannic
02-19-2005, 06:34
Check the timing as well, in combination with vacuum air leaks on the supply (from tank to pump) side of the lift pump and clogged fuel filters, it can play a major role in surging.
The rebuild shop had me check the fuel press to the pump. 7 pounds as it turned out. Put a clear vinyl line on the injector pumps return line to see if any air was going thru the pump. Saw a few very small bubbles at first and then nonthing. Ran for about five minutes with no air going into the jug. When I moved the throttle with my hand and held it, the RPM would not settle down. Rebuild shop wants to lookj at it so maybe they will come up with something.
Stray Cat
03-08-2005, 09:48
Did you ever resolve this? What was the resolution?
It went into the shop today. should hear sometime tomorrow. My last test was to place a vinyl hose between the filter and the I/P with a pressure gauge teed in. Runs smooth at idle with 8.5 psi to the pump, but as I pushed my finger down on the pump throttle lever the RPM increased to about 1000RPM and stopped. Continued to push for another 3/8 inch and then RPM increased suddendly to about 2200 and surged up and down about 50 RPM. Press to pump droped to 7 PSI. Pushed to 3/4 throttle and surging continued. Pressure to pump never below 5.5 psi and no Bubbles in line. Did this six times and the same thing occured. The Rebuild shop foreman was told the story and he is going to monitor the work. He is a 6.2 owner himself.
I will update when I get the word.
SteveMc
Hi Steve,
maybe temporarily bypassing the fuel filter can help to determine the problem.
For testing purposes just install a cheap clear plastic filter inline the fuel feed hose.
Just my two (euro-)cents.
Regards,
Walter
[ 03-09-2005, 06:28 AM: Message edited by: waorth ]
Two of the top fuel people in the shop drove the suburban and concluded the engine is doing just fine. Something in the pump throttling and the new gears, they think, are responsible for the
rpm surge I get as I accelerate. The occasion surging at cruse they believe is transmission related because the engine never changes its smooth running sound.
I am skeptical. The Transmission did take a hit when the crank broke from the looks of the flex plate. However, the other seems a little random to be normal.. I plan to drive it a while to see there are any chages and check transmission posts to see if anyone discribes the cruse surging. It is occasional and the vehicle is very driveable. I just like perfection.
Any thoughts I would be interested.
Stevemc
britannic
03-20-2005, 06:43
Try temporarily disconnecting the CDR valve and then drive for at least 6 miles or more and observe the symptoms. My CDR failed and I had similar problems with surging and uncommanded engine revving whilst driving - although it does seem more like the IP in your case.
Originally posted by SteveMc:
I just put in a gear timing set from DSG and while in the area had the old DB2 4544 IP overhauled. Have noticed now the engine wants to surge when I increase the throttle from idle. It also doesnt want to keep a steady RPM while going down the road at almost any RPM
Have changed the fuel filter and bleed the system finding no air. I think there is a governor seal that may have been installed incorrectly by the rebuilder however, wanted to see if any of this surging could be the timing gear set.
Going from Idle it will jump from about 800/1000 RPM to about 1400/1600 instead of a smooth increase. On the road I hear and feel the RPM changing more than see it on the TACH.
Any thoughts appreciated
SteveMc
Thanks for the note on the CDR valve Britannic.
The I/P is now in the shop where they overhauled it. They have the test equipment there to check everything out and the foreman was going to do the work. Said he may call me over when it is hooked up to see how it does. I hope he does because I would like to see it running on the machine.
SteveMc
Well the pump was gone over by the shop, all the bullitions doubled checked and then tested on the stand. I watched the test and the pump did just what it was suppose to do. Good timing movement, steady out put at all speeds, good governor responce, all checked out. Put the pump back in and still have the problem.
I changed the CDR valve and checked that the fuel return line was clear. Now I am moving the timing a half a line at a time to see if there is a difference.What on earth can it be. I think I will also call DSG to see if anyone else has had such a problem when gears were installed. Without knowing the history of the engine there may be something I am missing.
SteveMc
britannic
04-23-2005, 10:16
Re-check for a vacuum air leak on the supply side and also ensure that the lift pump is producing enough pressure and the fuel supply is free-flowing.
Is the gas cap venting properly?
Thanks for the suggestions Britannic. Checked out the fuel cap right away and it was ok. Am changing out the rubber lines in the steel fuel line this week. Problem is gettin worse, so something has to show its self soon.
Started a new post on finding the air leak.
SteveMc
britannic
05-01-2005, 05:49
Have you tried the 8-10psi fuel tank pressurization test yet?
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