First, a background on my truck:

1994 Chevy Suburban. Remanufactured engine 40K ago by previous owner, PMD relocated to front bumper with a heatsink. Homebrew WVO kit with heated tank, HIH, Raptor pump, heated fuel filter, FPHE, and separate lift pump for diesel (http://www.dieselplace.com/forum/showthread.php?t=358554#). Fuel pressure gauge installed with diesel pressures hovering around 10-12 PSI and WVO pressures around 9-14 PSI. Fuel filter changed and fuel screen in IP cleaned just last weekend.

I replaced my failing IP 6 weeks ago, with a used IP. You can read about my diagnosis Here (http://www.dieselplace.com/forum/showthread.php?t=358554). Main symptoms were codes 35 and 36, surging to 2200 RPM without the ability to slow the engine down, initially on just WVO but eventually on both fuels.

The new IP ran perfectly for over 2,000 miles, although it would throw a code 36 when I switched over to WVO for the first 2-3 minutes. Last weekend I drove 800 miles round trip. On the way there I had a lot of bucking at highway speeds and SES light on intermittently the whole way. When I arrived I ran the codes, 34,35,36,42. Also, from that point on, I've had hard starts with immense clouds of white smoke and at least 15 seconds of cranking necessary to start. After a minute of driving it clears up and the truck runs excellently. At the same time I developed the sticking at 2200 RPM again, not as severe as with the last IP but still noticeable and more often on WVO than Diesel. It only sticks if the transmission is in 3rd gear (automatic tranny.) Oddly, on the way back I had stellar performance for the first 200 miles, then a bit of bucking, but no codes at all. Later when doing around town driving I got codes 34, 36 and 42.

So, I'm thinking it could be timing. I never had the truck timed electronically when I replaced the IP, I just lined it up with a scribe mark. The timing could explain the white smoke and hard starts. My issue is, could timing cause the sticking at 2200 RPMs? Because if I'm going to need a new IP it doesn't make sense to pay someone to time the old pump just so I can replace it. Also, This Thread on a WVO forum (http://frybrid.com/forum/showthread.php?t=15681&page=2) suggests there could be an electrical malfunction causing the surging, although this guy's engine is a NA 6.5, and I'm pretty sure I don't have an ESS, but could there be something electrical causing the torque converter to lock up like it is doing to him?

Finally, I have no access to a scan tool, I am in Lisle NY 13797 if anyone is nearby and feels like helping me diagnose. I do have a spare IP, but I'd prefer not to use it. I am pretty frustrated at the thought of having to change out my IP every 6 weeks. Checklist is in the following reply.

2. Year of truck/engine. 1994 Chevy Suburban
3. Odometer reading (indicate miles or kilometers). 215K and 45K on the remanufactured motor
4. Indicate the model number on the Injection pump (starts DS4 or DB2......).DS4
5. Indicate if you know if it’s a 1500, 2500, 2500HD, 3500, 3500HD. 1500
6. Do you have an EGR on the engine? (An F or an S engine code 8th VIN digit) not sure
7. Air Filter condition (visual check). Clean
8. Fuel filter condition (freshly changed, mileage (http://www.dieselplace.com/forum/showthread.php?t=42248) since changed). Clean, both for VO and Diesel
9. Location of PMD/FSD (http://www.dieselplace.com/forum/showthread.php?t=39436)? (ex. on pump/remote over intake, behind bumper). Remote in bumper on heatsink
9a. If remote mounted, describe wiring harness (homemade or purchased from which vendor). Purchased
9b. Indicate the location and condition of the FSD/IP grounding wire. Screwed in near IP
10. Outside Temperature (C or F). 50-75F

11. Service Engine Light while running? Intermittent
11a. Service Engine light does glow during start/cranking/bulb check: Yes
12.Have you scanned for engine codes? Yes
12a. List exact results on engine codes (http://www.dieselplace.com/forum/dtc.php). 34,35,36,42 off and on.

13. Condition of Battery terminals (removed, cleaned and tightened). Good
14. Known condition and age of Batteries. Less than a year old.
14a. Are batteries a matched set of same age? No
15. Condition of Major Grounds (http://www.dieselplace.com/forum/showthread.php?t=157085) (removed, cleaned and tightened) Have not touched them.

16. Does engine crank, or "turn over"? Yes
16a. Does engine start and run? Yes
18. Does your Wait To Start light come on? Yes
18a.Number of seconds WTS light is lit. 7-10
19. Engine Cranking speed (if you have an accurate tachometer). As usual.

20. Are you experiencing Stalling? No.
20b. Do you notice loss of dash or instruments? No
23. Lift pump test (http://dieselplace.com/forum/showthread.php?t=39350) – Lift pumps are fine.

24. Upon cold start, does the radiator hose get hard quickly? Not sure
25. Upon cold start, do you have excessive white smoke? Yes
26. Do you have excessive cranking time before the engine starts? Yes
27. Have you used the block heater? Does it affect engine starting? Have not tried.
28. Are all glow plugs in proper working order (http://www.dieselplace.com/forum/showthread.php?t=39182)? Yes, tested recently and installed less than 6 months ago.

29. During hard acceleration, do you have excessive black smoke? No
30. Do you have any unusual exhaust smoke issues? Yes
31. Turbo check out (http://dieselplace.com/forum/showthread.php?t=39368) – Have not done this
32. Indicate fuel that you are using: Two tank conversion, D2 and WVO.
32a. If running Veggie Oil fuel setup, indicate details of your conversion
Homebrew kit with heated tank, HIH, Raptor pump, heated fuel filter, FPHE, and separate lift pump for diesel (http://www.dieselplace.com/forum/showthread.php?t=358554). Fuel pressure gauge installed with diesel pressures hovering around 10-12 PSI and WVO pressures around 9-14 PSI. Fuel filter changed and fuel screen in IP cleaned just last weekend.

33. Are you using any fuel additives? No
34. Upon unscrewing fuel cap, do you have a large vacuum formed in the tank? No
35. Do you have any service history available that might pertain to the problem you are having? See above

Nobody has any thoughts or suggestions?

What number pump did you replace with ? 5068 ??

Original (failed) pump: Not sure, can check later tonight but it was not a 5068.
Current (on the truck) pump: DS4-831-5488
Spare (on the shelf) pump: DS4-831-5521

94 takes 5067-5068 only.
can be run with a 5521 if you chance the ECM or chip with a 95 model.
It could well be the root of your problems

It's my understanding that only some '94 trucks use the 5068. I looked into buying a reman pump and they asked for the pump number and said I did not need a 5068. Also, since the engine was remanufactured, I assume when they did it they used the more current part and not the odd ball one year IP, but I could be wrong.

As per Diesel Care's website: If you have a 1994 we will have to have the part number off your injection pump as there are two for that application only.

Yes a 5068 is the only one that will work for the 94 .
Ask me how I know this .

Thanks to Bison for the help.!!!!
The 94 engine i installed into the 98 was having problems (fishbite) etc. Installed the 5521 pump last week works great now.

OK, how do you know this? How come all the sellers of rebuilt pumps say their pumps that work for 95-99 will work on some 94s? Also, when I bought it the pump that had been on there for 40K was not a 5067 or 5068, and I got 4000 good miles on it after i converted to WVO. The 5488 pump I have on there now was flawless for 2000 miles as well.

Also, if you put the 94 engine in a 98 then you should have the 98 ECM and therefore you'd want to have a pump that wasn't a 5068 right?

I went over everything on this 98 after i installed the engine from the 94 . . Grounds , pmd , computer , app (pedal) wiring etc. with no luck. !!

I had little to no control on the pedal from 1400-1800 rpms, it idle nice and smooth but if you tried to rev it up once it hit 1200-1400 it would take off up passed 2000. If you did a quick snap of the pedal it would go to red line then drop back to idle. Plus the trans did not shift right , some times was not bad shift point, next time it was the shits. Lock up was not working correct also . The tranny was so mushy that I order a shft kit for it ,

Bison put me on to the pump #'s , after see that it was a 5068 pump I called Bill Heath. bill said the 94 use's the 5067-5068 pump and would not work with the 98 truck. So I switch out the 5068 pump for the 5521 problems solved Runs like a top now. the tranny works great now too,

I had a hard time to believe that the pump # would have that kinda of affect.

It was a good lesson

Give Bill a call at Heath diesel. i found him very easy to talk too and deal with!!

But what you're saying is that the 5068 will not work in a 1998. That doesn't mean that the 5488 will not work on a 94. I'm saying just because it goes one way doesn't mean it goes the other way.

The original pump, the one that was on there for 40K of diesel and 4.5K of WVO/Diesel was pump # DS4-831-5521. I had the surging/sticking symptom with both the original 5521 and with the current 5488. Both worked fine for a while though. Any more insights?

I was told that the 5068 is the one and only for the 94 .

On this 98 the more miles i put on it the worse the problem got

looking at bill's web site if the later pump 5521 would work on the 94 model I would think they would only stock the one. IMO

Good luck i will be watching to see how this plays out

On heathdiesel.com he says the 5068 is for 1994 only, but also says that the 5521 is for 1994-2000. I know they switched a lot of stuff during 1994, whenever I go in for parts they ask if it's a 1994 or 1994.5, even for little stuff like headlights. Is it possible the 5488 won't work when the 5521 will? What is the difference?

Seems like you have a hard time believing a know fact.

The 94 model had the first Electr IP.two models as been said have been used ,the 5067 and 5068, they wont work in any later yr truck,but You can swap to a 5288 or 5521 in a 94 if you use a 95 yr ECM and/or the Chip cause they are both OBDl .
96 and up is OBDll
You can plant a 94 engine in any later yr veh if you use the later IP,anyting but the 5067/68.

Maybe the PO had swapped both IP and ECM allready?

5068 fit only the 94 Heavy Duty truck. ( Non EGR model )

I'm not trying to be beligerent, Bison, just ignorant is all. I don't have a book of facts, unfortunately, I only have a group of people many who are more knowledgeable than I, to ask questions of. When I look at the websites that sell IPs for the 6.5 they say some 1994s had the 5067/8 and some had the 5521. I'm saying my truck, when I bought it a year ago, had a 5521 with no known issues. Then, later down the road, that 5521 had problems, many on this board attributed those problems to a worn IP. I replaced the IP with the 5488 and my symptoms went away. 2000 miles later the symptoms came back, eerily similar to before.

Revx1000 says he had a 94 engine with the 5068 on it in his 99 and it had problems which got progressively worse. In my mind that could be a bad IP getting worse or a compatibility issue between the truck and the IP, or perhaps a lurking variable.

If I had these issues immediately after putting in the 5488 and I knew the 5488 worked well on another truck that would be one thing, but since the symptoms are evolving, getting worse, and since they were non existent for 2000 miles, I'm skeptical that the issue is compatibility of the truck and the IP.

What is the difference between the 5068, the 5521 and the 5488? Is there a number on the PCM I could check to see which pump it is compatible with?

I have a buddy with a 94, the dealer swapped he IP with a 5521.
The truck ran fine,but had no power and was hard starting.I swapped the ECM from a 95 in and The problems disapeared.

so it seems there are a host of diff problems that can occur when the wrong IP or ECM are on the 94's.your best bet is to either get a 5068 or try to find a 95 ECM from a truck with the same tranny as yours.

What I'm saying is that perhaps he had a 94 with the 5068 and it couldn't handle the 5521, but I have a 94 with the 5521 and it can't handle the 5068. I'm pretty confident some 94s came stock with the 5521. That being said, is there a way I can check the PCM to see what pumps it is compatible with?

Also, you guys keep talking about the 5068 and the 5521 but no mention of the 5488 I have in there. In what situation can I run the 5488?

By my books there aint a 5488.
The 95-96- 97-98 used the 5288
the 99 used a 5459
2000 and up and all yrs replacement except the 94 are 5521.

The 5521 did,nt exist in 94,it was born in 2000.

You all know far more than I do about these rigs but I can tell you I have a 1994 Blazer that had a 5521 on it that I just replaced with an overhauled 5521. It now runs perfectly.

Bison I have a 94 van and i put a 5521 pump in it. go a code 14 31 42 57 58. Do you know where i can get a 1995 computer for it a reasonalble price? If You think that is what i need? I have the 4L60E trans. As far as I have checked at this time. Thanks for you help on this!....Simon 6.5 #1.

All you need is an EPROM from a 95 with the 4l80 tranny.
Yunkyard or auto supply store,or get a performance chip while you're at it.

You all know far more than I do about these rigs but I can tell you I have a 1994 Blazer that had a 5521 on it that I just replaced with an overhauled 5521. It now runs perfectly.they must've swapped the Eprom when they put the first 5521 on.

Yes you are right. I checked this out today. In fact I have a label on the ECM itself that shows it is a Delco overhauled unit with a date of 1995.

Pat

It must be specific to the flash of the PROM in 1994. I bought a used pump from a 94 that had a 5521 installed by the dealer when the original 5068 failed. I didn't purchase the PCM from the guy because he said it was the original 94 PCM. Owner claimed the truck ran great... so great that he snapped the crank. The guy was a maniac so who really knows. The 5521 was definitely running that 94 though.

Edit: I just noticed on your check list that you haven't removed and cleaned the ground wires. If your PCM ground is poor it could be causing a whole slew of issues. Also, check the resistance at your crank position sensor (950 -1050 ohms at the pigtail going to the sensor between pin A and C)

In my case it just so happens I have a PCM with a 1995 date code which presumably means the EPROM is also a 1995. I talked to the folks at Heath Diesel Power today because I ordered a GL4 and they informed me (as others have said) that a 5521 will work with just an EPROM change to a 1995. Based on what I've learned here and from Heath it would seem you must at minimum have a 1995 EPROM as well.

Pat

Where are you located Nicky? I have a couple spare 95 PCM's that I could send you a Prom out of. Both PCM's are bad because the TCM's are faulty. Neither will shift because they're not detecting Input speed sensor voltage. I'd be willing to send one to you for diagnostic purposes... if you send it back of course :)

What is a Prom? My PCM is behind the glovebox right? will it say what year it is, or can I use a part # on it to see what year it is?

The PROM is located on the bottom side of your ECM --carefully pull the ECM out and flip it over. There is a panel on the bottom side fastened down with a T10 torx screw. If you take that out you will see the PROM (or EPROM whatever it actually is).

If you do take yours out and replace or test your ECM with another, be careful as you extract the PROM. You'll want to gently lift one end and then the other, and then the other, etc so as to not break one of the legs. Also note the proper orientation when inserting replacement PROM.

after rechecking the serial # on my IP I'm pretty sure the pump in there is a 5459. I'm positive about the 5 and 4, the other two are difficult to read.

If I changed my Eprom to a '95 could I keep my 5459 or would I have to put the 5521 in there?

Bison I have a 94 van and i had a 5521 pump in it installed in 2001 I checked. got a code 14 17 18 31 42 maybe 57. It would run but never get warmed up before it stalled so I put a IP1 Standard rebuilt pump and PMD in it have codes 14 31 42 57 58 I hooked up the old pump got codes 14 31 42 57 58 they didn't change??? On a van the grounds are different than on the pickup trucks I took all the grounds off [one back passenger side, one drivers side front of motor side of head and the grounding block] and cleaned them the grounding block bolt by the fuse box was loose i put a bigger bolt the to hold it tight i got a code 12 after that plus the new ones but no more code 12's. I put a new mechanical lift pump in it changed the fuel filter new batteries and cleaned the terminals the solenoid clicks when i hook the plug up i have diesel at the line going into the injector pump with the lines broken loose at the injectors there is no fuel coming out. I wonder if I have computer problems? Code 57 is a 5 volt short i have 5 volts coming out of the computer. I was told to check the PMD harness unhooked from PMD A to ground while cranking there should be 1.6 to 1.8 volts. terminal C to Positive battery terminal test light should light terminal D to ground should light test light. If any of these test fail then the injector pump is bad. How do i check for a 5 volt short? Do you have any other Idea's? Do you think the computer is not working right I just can't under stand why there is no Diesel coming out of the pump. What should I do next? HELP!!