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Stalling / Smoke

dbrannon79 said:
Need to get the clear hose on the return line off the IP and look for bubbles in the fuel system. also need to verify the LP is in fact supplying fuel pressure to the IP. get you a pressure gauge installed at the IP inlet and watch fuel pressure at idle and then how it acts when it is bogging down. You could be loosing the LP intermittently, which will also in-turn allow the IP to bring the lines back to the tank into a vacuum and or suck air into the system.

not to mention a possible clogged sock on the pickup tube in the tank. if someone has ever had the tank down, possibly replaced the sock with one not made for diesel or has the factory one that's just clogged. this can also cause the same thing as a failing LP. can also kill the LP and IP too.
Click to expand...
He already ordered an LP and filter. He should have them today.
 
Well it looks like the issue ended up being a dirty fuel stock/strainer. Took it off and put a fuel/water separator between the FSU and LP. It appears to be working fine. Don't think it is a clogged soot trap. We'll see in the morning after testing everything out.
 
So buttoned everything up and reconnected the downpipe and soot trap (Didn't gut it yet) to see if that fixed everything. Unfortunately it didn't. It stalled out again, so I'm thinking it may be the soot trap still even though the LP and strainer were bad. Disconnected the DP and Soot trap and it doesn't stall. One thing we noticed at idle with the A/C on the RPM's fluctuate between 500-800 back and forth. Going back and forth with 2 different trucks. Pulling my last hair out of my bald head.
 
refresh my memory again. this was a 95 with a electronic DS4 IP? or the DB2 mechanical?

Mine will change a touch on the RPM with the ac turned on. the PCM senses the extra load and gives slightly more fuel to compensate for the load.

when the RPM changes is the compressor cycling? usually the PCM is a tad slow to respond. I have loaded mine down with the AC and steering the wheels to the lock. when it loads the RPM will drop around to 500 or so then the PCM responds, up goes the RPMS.

for a mechanical DB2, there is a idle solenoid on the throttle linkage at the IP. when the AC is turned on, that solenoid is supposed to bump the RPM a little. I'm not certain if it cycles off and on with the compressor or just stays on.
 
dbrannon79 said:
refresh my memory again. this was a 95 with a electronic DS4 IP? or the DB2 mechanical?

Mine will change a touch on the RPM with the ac turned on. the PCM senses the extra load and gives slightly more fuel to compensate for the load.

when the RPM changes is the compressor cycling? usually the PCM is a tad slow to respond. I have loaded mine down with the AC and steering the wheels to the lock. when it loads the RPM will drop around to 500 or so then the PCM responds, up goes the RPMS.

for a mechanical DB2, there is a idle solenoid on the throttle linkage at the IP. when the AC is turned on, that solenoid is supposed to bump the RPM a little. I'm not certain if it cycles off and on with the compressor or just stays on.
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This is the 98 DS4. Never noticed it in 7 years. I have always heard it bog down slightly when the a/c is on but the RPM's never fluctuated back and forth continuously while on at idle.
 
Try running the AC off of max, put the controls to fresh air.
At least on my truck that causes the AC compressor to run full time. On MAX the compressor cycles on then off several times in a minute.
See if Yours compressor does not fluctuate on fresh air mode and see then if the RPMs fluctuate.
 
Wait- there is an a/c setting other than max recirculate?

My work truck an 08 c3500 dmax - every time I start it or even accelerate hard it defaults to fresh air. HATE IT. I keep wondering about pulling plastic and unplugging a servo -
But can’t remember how involved that is on this rig.
 
Will L. said:
Wait- there is an a/c setting other than max recirculate?

My work truck an 08 c3500 dmax - every time I start it or even accelerate hard it defaults to fresh air. HATE IT. I keep wondering about pulling plastic and unplugging a servo -
But can’t remember how involved that is on this rig.
Click to expand...
Did GM use the same concept on the high pressure switch to open the recirc door? I never saw or understood why they did that, because when hotter air hits the evap coils, the pressures increase. I need to look up the pressure specs when it opens and closes the contacts, but I would think a compressor cut out switch would be better served over that recirc door pressure switch.
 
Haven't had time to do anything on this lately. My son thinks it may be the injectors. I'm kind of thinking that because they have about 125k miles on them. Any way of confirming that without taking them out and into a shop for testing?
 
not entirely, but if the injectors have over 100k on them, it's time to replace them anyway. you can pickup a cheap pressure tester and test them yourself, watching pop pressure and atomization spray patterns.
 
Thats a good price. I been planning to put one together hut at that price I am just gonna buy that and add my liquid filled gauge as one option -The gauge that comes on that is up 8,700 psi. Hard to get really accurate readings with that. Look at the close up screenshot of their pic: now imagine trying to get within 25 psi… is this 1200 or 1225?IMG_8665.png

When picking a gauge- understand 2 things:

1) like a torque wrench, always get one rated as close to the “in use” range as possible for accuracy. Dont get a 10,000 psi gauge when 5,000 will do. It isn’t better- it is twice as bad. And since a 3,000 psi gauge will do, it is over three times worse.
1% accuracy x 10,000 psi means off by 100 psi. But one time it might be 100 psi low, and the next time 100 psi high- so your real results might be off by 200 psi !
A 3,000 psi gauge with same accuracy is 30 psi off so max of 60 psi difference.

2) $ will definitely affect how accurate you get your adjustments to. Mechanical gauges are far cheaper to make. But almost never can achieve great accuracy without spending a couple hundred dollars. It takes a book to explain why. This is why most things of critical requirement is now digital. A digital gauge might cost a little more but one that has a peak setting will tell you an exact (within gauge accuracy) pressure where it popped.
So here is a low cost gauge:
$59 for a digital gauge with peak recording that has 3600 psi ability- but has a 1% accuracy rating. 3600 X 1%= 36 psi it could be off. One time it might read 36 psi too low and the next it might read 36 psi too high so really you might have 2 injectors that are perfectly exactly the same but read 72 psi different/ or they are 72psi different and read the same. Not within our desired 25 psi range even if you take the time to get them exact- which most people read a gauge and say the gauge is within 25 so they are good when they don’t account for gauge inaccuracy. Yes needle is more accurate but it is up to your eye and brain to be accurate and say “that MOVING NEEDLE LOOKED LIKE X”. So unless your gauge has a peak marker getting pushed by the needle- and really accurate mechanical ones with a marker are over $400 that I have found. So imo digital is the way to go.

Here is a 6000psi at 0.5% accuracy so 30 psi low or high means maybe off by 60 psi total for $100 by same manufacturer. Is $40 more worth being 12psi closer? Individual choice.https://www.amazon.com/XZT-Hydraulic-Pressure-0-6000PSI-4BSP-Base/dp/B0148M9XQM/ref=mp_s_a_1_28?crid=1RTBICTG13768&keywords=digital+hydraulic+pressure+gauge&qid=1693063362&sprefix=digital+hydraulic+%2Caps%2C151&sr=8-28

Here is one that meets our spec of desired within 25psi of each other.
5000psi and 0.25% accuracy range so 12.5psi error range x 2= 25psi low to high, for $185. Also note it actually lists our media instead of just hydraulic oil. To me, the added cost makes it worth it. But spending a bit more gets you more accurate.

The same company makes a 3000 psi gauge with same accuracy so 7.5psi high or low meaning you can get within 15 psi of each other IF WILLING to take the effort. It is a lot of effort, believe me. That gauge was just under $200 but they are out of stock. I am waiting for them to get more and hope price is good. $200 is my desired range a d want that accuracy. But I don’t need it right away. So I just check once in while.


Remember always check the media, one rated for only air pressure is gonna die before you get through a set of injectors. And a gauge you cant get accurate readings on might tell you all is good when they are not- or might have you adjusting pop pressures that were good and now are worse. Guy I know has spent an entire day chasing perfect balance when his gauge sucked.
 
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