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s3construction

Apps, Ecm, Pump, or something else?

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Ok I just bought a 99 dodge 3500 24v Cummins with 222,000 miles I have searched but cant find nothing with same symptoms like mine exact.  When you barely touch pedal it revs really high when in park.  When you try to drive it it takes off really good then dead pedal then picks back up after it falls to around 12-1500 rpms and goes again it will not stay at a constant speed.   Try and it cuts out till rpms fall them picks back up again.  It appears the pump is not the original, and the guy I bought it from had it at a shop trying to get it fixed and they said they tried a different apps. But I dont think they know much about these trucks.  Any ideas?  Also I have a problem with IOD fuse it blows the instant fuse touches but when I first test drove it the radio and stuff worked fine no problem but he did say it had IOD problem.   

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Question is the wait to start light coming on instantly with the key or does it have delays?

You might test for AC noise issues from the alternator first off.

What you describing is a ECM issue more so than a VP44 or APPS sensor issue.

As for the IOD fuse that has like the radio memory, door light and things of that nature on it.

(Fuse 12) power-dis.pdf

Edited by Mopar1973Man

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Another trick to try to verify the alternator. Unplug the field lead on the back of the alternator (2 wire). Then remove the alternator fuse. Don't unhook the BATT lead on the alternator you risk blowing the alternator fuse just better to remove the fuse. Now go for a test drive and see if the weird problems continue or not.

Another thing no one has ask is there any error codes? Just because there is no CHECK ENGINE light doesn't mean there isn't codes stored.

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Key trick doesn't work for 99. You must use a code reader to pull codes. The only year that actual works correctly is 2002 for the key trick. 98.5 and 99 don't work at all. 2000 might work but typically only shows the PCM. 2001 is also another year that might work and might not again only showing the PCM. 2002 will show both ECM and PCM.

http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/26-engine-systems/89-obdii-on-board-diagnostics-diagnostic-error-codes

Edited by Mopar1973Man

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I had similar issues when my ECM went, but my truck was undriveable. It also surged alot while idling. The really weird thing was while checking DTC's I had a list a mile long but none pertaining to the ECM. So post back what you find and dont be surprised if the list is long. 

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Unhooked alternator wires and took out fuse no difference.   I did notice when I turned key on this morning very first thing there was a delay in the wait to start but it seems like its only after trucks been sitting.   

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ECM memory issue. If there is any delay to getting that WAIT TO START light to come on then the on board memory is damaged and its having issues booting up. This again points back to a damaged alternator. So then the weird throttle control is because the boot process is loading EPROM and the data is becoming corrupt on booting.

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So new alt and ecm?  Also hear a thump when turning key on guessing that may be in the hvac system?  

Also it does take alternator along time to get up to 14 on the charging system when you start truck via the in dash guage

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Are you confusing the delay (miss communication here)? You should hear the clunk because that is the grid heater relay going on, doing it's job. Then the wait to start lite should stay on a little while till grid heater (heats intake air when cold), then wait to start lite goes out like it should and then you start the truck. Then grid heater cycles on and off after you start (clunk sound) never allowing the volt meter to get up to the 14.2 volts till grid heaters decide truck has run long enough for warm up. Volt meter should go up and down till they shut down and then it will gradually climb to full charge reading around 14.2- 14.7 volts. after heater shuts down

The weaker batteries will take a bit longer to let the gauge climb back up but also drop more drastic when heater cycles, if weak.

I would not jump to any big expense yet... not till you get good batteries with all electrical connections nice and clean. You will need to get a Timbo Apps for reliability any how.... about $150... so try that first also.

Now I think I'M in big big trouble undermining Michaels advice hear... but... I see this miscommunication going on.

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14 minutes ago, JAG1 said:

Now I think I'M in big big trouble undermining Michaels advice

No... JAG1 is on the money...

I typically work a two smoking gun rule in regards to parts. So far we got a weird throttle issue that point towards the ECM having issues. As for the alternator that would be cause of the ECM if so. But still no testing of the alternator has be done to verify anything. The part of the test you have to pay attention to is the AC voltage output. So if you start the truck and using a DVM and probe the BATT terminal on the alternator and the alternator case. Make sure you have a DVM that can measure down to 2 volts or less. The AC voltage should measure about 0.01 to 0.02 normal. 0.05 is marginal and might create issues. Anything above 0.1 is a fail.

Grid heater will and do pull more power than the alternator can produce. When both elements are running its a 190 amp draw vs only 140 amp charge rate. 

As for the APPS... That I would look for a error code and see if anything pops up. If the APPS is damaged it will trip a error code but not always will it set the CHECK ENGINE light. Or if you got a live data tool you can watch the TPS value and see if it has weird spiking occurring.

Edited by Mopar1973Man
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Thanks Mike. It does take awhile for alternator charge to get back up on it's full charge. Electric lift pump is drawing a load also. I had a weird throttle response at one point and had the Timbo APPS in the glove box. Changed it out and that went away.

Michael is on the money as well... need to test the alternator for excessive AC noise but you must have one of the expensive volt meters to test. Otherwise you can only test for DC output should be around 14.2- 14.7 after truck grid heater stops drawing load. Takes awhile.

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I didnt THINK I misunderstood.?:think:. After truck sets for awhile like overnight it takes awhile for the wait to start light to come on.   Seems like after the initial start and run for a few mins there is no delay in the wait to start like to come on with key.   I understand the clunk now that you told me and I get why the guage takes a min to get up to 14 as well now that you told me that.   We was thinkin ecm or apps from the start kinda hoped the apps may just need calibration.   I had no idea of the finicky ways these trucks seem to have after reading all the forum stuff here and at the cummins forum I thought they were tough as nails half million mile change the oil and filters motors, and maybe they are after a few upgrades like the Timbo Apps and fuel filter system and alternator etc

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I'm keepin' my fingers crossed that it is weak batteries/ weak connection first and next would be a burned diode in the alternator.:pray:

I read once about a guy that had a bad lift pump drawing excessive load and had your symptoms as well. It showed how important to have a clean electrical system and not have the lift pump connected to the ECM like the factory does.

Can you tell us what your fuel pressure is while running? What lift pump you have?

Hoping I'm on the right track otherwise I'll get a good bonk on the head, might get worse than that when I go visit Michael again.:ahhh:

Edited by JAG1

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Pull the trouble codes and post them. Then you can get a better idea of where to start. Just throwing parts at it will get expensive quickly. Some more info on the truck would be beneficial also. Such as any upgrades from stock, gauges, fuel system, and such.

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From just what Ive played with the truck not having it run much I have had to jump it couple times to get it to start today so Im gonna throw couple fresh batteries on and clean cables and grounds real good start there.   I will be able to check fuel pressure later in week when I get some more time to work on it.  Thanks guys 

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Be sure the ground going to the block is clean and tight as well. I think there are 2 of them from ea. battery

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After new batteries chasing numerous wires cleaning grounds etc no change in problem.  So a friend of mine owns a salvage yard and he had a used ecm we changed it and it runs perfect now.   Thanks for the help and point in right direction

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