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-   -   Odd issue.. (https://www.dieselplace.com/forum/63-gm-diesel-engines/21-6-5l-diesel-engine/812202-odd-issue.html)

Towers91 02-23-2016 11:24 PM

Odd issue..
 
1999 gmc suburban heavy half, 6.5 200k kms on it, 4x4

Not really sure how to diagnose, but i think its my lift pump, so im just gonna start from the begining of my troubles. Had weeping fuel lines, and replaced them, but in diagnosing the lines i ran the lift pump of lubrication (got a code) dont remember the code, but it said somthing about fuel pump lubrication, kept sucking air, after the lines were replaced every time id bump the key into run mode id hear the pump under the drivers door sounding a little like a clicking sound, but itd fire up and idle for an hour if needed.

I moved to a new shop today and loaded the burban full of shelving and tools and set forth to the new shop, got down the street and it died when i turned on the radio. Now every time i bump the key i get minimal pressure out of the fuel filter valve, and no clicking under the drivers door, which leads me to believe the LP went on me. No biggie if it did, but i dont want to go chasing an issue that im not 100% on the cause of said issue. Im new to diesels, and unsure where to start with diagnosing.

Freddyack 02-23-2016 11:43 PM

As far as I know, there is no code for a faulty lift pump.

Check first to see if the lift pump is connected to the lift pump wiring connector.

If you can find this: https://www.dieselplace.com/forum/63-...ml#post6910025, apply 12v and open the water in fuel drain by the thermostat. Make sure to have a container to capture fuel. If you get a steady stream of fuel the lift pump is working.

If the lift pump works, then there is a problem with the lift pump relay or another electrical short.

JMJNet 02-23-2016 11:46 PM

Well, you can take a chance and replace the LP and go from there.

Also, check the batteries.
If LP goes, cranking takes longer, batteries gave up.

Towers91 02-23-2016 11:55 PM

Ill have to try that out, but i believe itd still be hooked up under the truck, i havent messed with it, but ill try it, what would the lubrication code be? Ill go down and see if there are any previous codes stored so i can tell you exactly what the code was.

OkDually 02-24-2016 09:22 AM

Quote:

Originally Posted by Towers91 (Post 8140906)
Ill have to try that out, but i believe itd still be hooked up under the truck, i havent messed with it, but ill try it, what would the lubrication code be? Ill go down and see if there are any previous codes stored so i can tell you exactly what the code was.

There is NO code for the Lift Pump failure.

If you suspect there are codes, get a scanner and read the codes and post it here for us.

JMJNet 02-24-2016 09:29 AM

A lot of things in this truck does not code, even for a 99.

For it to code, there should be a sensor of some sort.
There is no sensor in the Lift Pump or PMD.

A lot of codes are to warn about Injector Pump conditions or boost condition.

Towers91 02-24-2016 06:25 PM

Im gonna replace the LP tommorrow evening, and if i still have the same conditions, how would i go about checking the injector pump? And whats the likely hood of it being just a clogged filter?

Towers91 02-24-2016 10:31 PM

Well, i went out and bought a lift pump, probably gonna install tmrw, but i now have a clacking sound coming from under the drivers door again, it was there yesterday when i cold started, and when it died i didnt have any clacking, batt was too dead to turn over, and was wearing good clothes so i didnt check pressure, but i scanned the codes to see if any had stored, and had no previous codes. So i cant actually tell you exactly what code it was.

OkDually 02-25-2016 09:03 AM

Quote:

Originally Posted by Towers91 (Post 8142954)
Im gonna replace the LP tommorrow evening, and if i still have the same conditions, how would i go about checking the injector pump? And whats the likely hood of it being just a clogged filter?

There are lots of other things to rule out before you condemn the IP.
A properly cared for IP will last you 250,000+ miles... Change the fuel filter, Clean out the screen Manager inside of the bottom, center of the Fuel Filter manager.
When your down in there, inspect the bottom and if it is full of crud the best thing to do is to pull the whole thing out and clean it.

If you have any doubts about the screen manager you can replace it.

Stanadyne #29244

HeavyChevy95 02-25-2016 10:07 AM

Actually.. On OBD2 models, the Lift Pump is monitored, at least its voltage (amp) is..

Intermittent P0231 code


P0230- Fuel Pump Relay Control Circuit
P0231- Fuel Pump Secondary Circuit Low
P0232- Fuel Pump Secondary Circuit High

More info on
P0230
P0231
P0232


As I understand it.. The PCM notes the LP voltage (amperage draw) during Startup Mode, and uses that reading to monitor the LP performance for the duration of that ignition cycle.. Thats why alot of LP failures dont SET DTCS, during STARTUP MODE, its noting the skewed voltage reading of an already struggling and/or damaged liftpump..





The IP is the last of a long list of possible suspects.. Dont be so quick to convict without all the FACTS. Rush to judgement often compounds the pain and suffering of a costly misdiagnosis..


Good Luck..


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