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RmGuY0708
08-22-2007, 08:07 PM
I have a 1994 Chevy 2500 4x4 6.5td and I have codes 32 and 33. When I speed up in the truck the service engine light stays off, but when I let off or put it on cruise the light shows up. Those codes are both codes involving the EGR. Also, am I supposed to be getting 11-12mpg with this truck? Could the egr being bad have anything to do with my poor mileage? I am gonna test it with a vacuum pump to be sure if its good or bad. What all could be makin this suck fuel so bad?

young_gun
08-22-2007, 10:54 PM
hey you have pretty much the exact same problem as me...same truck too! i've changed solenoids and vacuum lines with no better results. i'll be watching this thread with hopes of some input.

grancito
08-23-2007, 12:09 AM
Disconnect the vacuum tube and put a bolt in the end of it, did that on my Chev 15 years ago. RmGuy the exhaust gas is probably being returned when you have power on, and therefore there is not enough air to burn the fuel. See my MPG below the 17mpg is highway 75 plus mph. Young Gun, the exhaust gas return could be useful for you in winter, disconnect it in summer. I understand that the 94 will not post a code when the tube to the EGR is disconnected and blocked.

Chevylover
08-23-2007, 12:46 AM
I understand that the 94 will not post a code when the tube to the EGR is disconnected and blocked.


All WITHOUT a MAF Sensor between airbox and intake should not show a code after disconnecting the EGR valve. OBD-1 do definitly notshowing a code, OBD-2 (after 1996->) somtimes, could be, but not a must.

Cu,
Sven

grancito
08-23-2007, 01:18 AM
Sven, are you talking about a connection to the MAP sensor on the fire wall, or the turbo pressure sensor on the air intake extension?

Chevylover
08-23-2007, 06:39 AM
Sven, are you talking about a connection to the MAP sensor on the fire wall, or the turbo pressure sensor on the air intake extension?

NO ! There are three sensors.

1.
The MAP sensor (also as EGR/Baro Sensor known) is in every 6.5TD from 1994-> and at the firewall as you mentioned.

2.
The Turbo Pressure Sensor is in every 6.5 with turbo on the intake near the place, where Walt recommends to mount the PMD cooler.


And last but not least :

3.
THIS IS A MassAirFlow - SENSOR :

http://www.ssdieselsupply.com/images/products/fullsize/79--20050206232657.jpg

Between stock airbox and turbo inlet and only in 1997 + 1998.



Cu,
Sven

jamesvtr
08-23-2007, 09:42 PM
my 99 had one before the reflash

young_gun
08-25-2007, 05:10 PM
I understand that the 94 will not post a code when the tube to the EGR is disconnected and blocked.

would this be the tube that runs right up to the valve on top of the intake? if so, i blocked it and erased the dtc's.....didn't help any.

grancito
08-25-2007, 09:03 PM
Yes that is the right tube, your code 33 is saying that the baro sensor on the firewall is faulty. You will still get a code until that is replaced $65 or see what www.rockauto.com says

RmGuY0708
09-19-2007, 07:54 PM
Well I got it figured out, it was a bad vacuum pump I had absolutly no vacuum at idle while it is supposed to have 18 inches of mercury. At 1500 rpm my pump was only pulling 5-6 inches of mercury.Ill tell you how much this effects my fuel mileage in a week or 2.

ddamrath
09-25-2007, 01:26 AM
my 99 had one before the reflash

What does a reflash do? How is it done? Thanks.

ddamrath
10-23-2007, 03:18 PM
Do I block the tube leading to the EGR valve itself so that nothing gets to the valve, or block the tube leading to the egr solenoid which eventually leads to the EGR/BARO (MAP) sensor on the firewall? I also have the MAF sensor. I've been coding 0401 for months, even after new IP, vacuum pump, EGR/BARO sensor, and the other three related solenoids. Truck runs fine, but the SES light is annoying.
-Don (98 6.5T, 99K)

grancito
10-23-2007, 09:36 PM
Block the tube you take off the EGR valve then vacuum is not lost.

ddamrath
10-24-2007, 11:32 AM
Thanks. I'll give it a shot. This site is a trucksaver. So, since I have your attention... truck doesn't seem to run quite the same since new IP installed 500 miles ago. A stealership replaced it under GM warranty and I'm thinking they didn't re-time it. Would bad timing cause hesitation in acceleration and turbo spooling at med-high speeds (40-65mph)? It's also knocking a bit and get a small puff of black smoke at first start-up of the day. With 99K I consider the little smoke normal. Idle SEEMS ok. MPG might be down a bit. I bought new marine injectors from Walt but haven't installed yet - want to get timing checked and set if needed first. Thanks.
-Don
98 6.5T, 99k, new IP, Vacuum pump, 4 inch exhaust, air intake

Chevylover
10-24-2007, 02:15 PM
What about your liftpump ? Also new with IP or not ? If not, could be possible, that the liftpump isn't working as it should. You should check it, because a bad liftpump CAN cause IP failure. Open the bleeder on the diesel filter while igniton on WITHOUT engine running. If fuel comes out of the bleeder, the liftpump is good.

Or while engine running, open the water-in-fuel bleeder (running a hose in a canister) at the thermostat neck for about 10-20 seconds and wait if the engine dies or not. If not, everything okay, but if it dies, the liftpump is bad.

Cu,
Sven

torque454
10-24-2007, 02:33 PM
What about your liftpump ? Also new with IP or not ? If not, could be possible, that the liftpump isn't working as it should. You should check it, because a bad liftpump CAN cause IP failure. Open the bleeder on the diesel filter while igniton on WITHOUT engine running. If fuel comes out of the bleeder, the liftpump is good.

Or while engine running, open the water-in-fuel bleeder (running a hose in a canister) at the thermostat neck for about 10-20 seconds and wait if the engine dies or not. If not, everything okay, but if it dies, the liftpump is bad.

Cu,
Sven


The pump will only run for a second or two with the key on and the engine off. That'd be an easily misleading test. You can open the bleeder a little with the engine running tho. Dont open it much because the lift pump really moves the volume and you could soak everything with diesel with that really easy. And well, since diesel is flammable, that'd just be bad. Fuel will for sure come out then if the pump is running. You can also open the one on the thermostat housing with the engine running and fuel should come out within just a second or two. Its got a hose attached to the bottom so it runs out on the ground. You dont wanna leave it open long in case the lift pump isnt working. I made that mistake once and it stalled and would not start again until the lift pump was replaced. $145 with me installing it (OEM replacement part) The reason was because there was air in it and it couldnt be bled out without the lift pump working. If no fuel flows it could also be the oil pressure sensor bad. If its bad the pump wont pump either.

ddamrath
10-24-2007, 09:20 PM
ok thanks. Where exactly will I find the thermostat housing? I'm rather new to this do it yourself mechanic work.

ddamrath
10-25-2007, 01:11 PM
Thanks. I feel kinda dumb for asking where the bleeder on the thermostat is... but I got it.... I opened the bleeder on the thermostat neck for a good 10 seconds at least and plenty of fuel came out with no stall. closed bleeder back up and truck continued to run.
I guess its time to get 'er hooked up to a scan tool and make sure the timing is right? Stealership claims they lined up the new IP when installing but did not hook the engine up to the scan tool to check it.

jamesvtr
10-25-2007, 09:11 PM
What does a reflash do? How is it done? Thanks.
i got a reflashed computer from westers . it got ride of egr and mass air flow sensor. gave me horse power and drive ability and most of all my pain in the ass egr code. you can buy them from ssd, westers and heath diesel. best money spent after exhaust and intake and gauges of course