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Question.

V

vintex

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Sunny queensland
got a question you may be able to throw some light on ,iv recently done a DB2 conversion on my 98 6.5
Massive hassles with the tranny until I got a quick 1 TCM
Any way iv noticed the od power spike when driving in town ( iv only done a couple hundred Klms since the conversion)
The engine will hit about 3500Rpm with no no load and then it starts to miss iv changed the fuel filter ,I'm not running the factory GMC filter as they are hard to get and expensive over hear.i thought this would fix the problem but it didn't so i moved back to the electric lift pump . I found this to be very hot to the touch ,iv used these tic tic pumps on many machines before and have never experienced heat before, cavitation came to mind so I put air back down the line and cleared any blockages that might have caused any problems,still the same result ,missing at high rpm,I'm thinking my lift pump may be rooted
Are there screens in the lift pump?? That may need flushing
I've noticed a small amount of air in the filter head when the vent screw is released ,just after the engine has been stopped ,this is what has led me to think my lift pump is the culprit
Please tell me your thoughts
Regards chris
 
Theres a screen inside the tank on the pickup that is known to clog up. Many do away with it, and install a 30 micron spin on pre filter setup so you dont have to drop the tank anymore.
 
You stated 3500 rpm.... you are more than likely getting into the governor in the db2... without pump work it will start to defuel around that rpm....
 
Thanks guys
The tank filter was done not long back,I used 3/8 fuel line to suit the filter that I had,the injectore pump was of a 6.2 it's been turned up to run a 6.5 so it's pretty standard inside,don't get me wrong I don't drive at 3500rpm, I try not to go over 2000rpm I'm like driving miss daisy
Thanks heaps
 
Listen to the above, also I would get a clear line on the return side of the ip for ensuring no air. Get a fuel pressure pump on the inlet side of the pump that not only reads pressure, but vacuum as well. Too much pressure in a db2 will advance the timing, and can do damage, but also will cause high rpm stuttering.
I run my db2 engine at 3,000 rpm all day long.
 
Will L. said:
Listen to the above, also I would get a clear line on the return side of the ip for ensuring no air. Get a fuel pressure pump on the inlet side of the pump that not only reads pressure, but vacuum as well. Too much pressure in a db2 will advance the timing, and can do damage, but also will cause high rpm stuttering.
I run my db2 engine at 3,000 rpm all day long.
Click to expand...
Could my timing be to far advanced? Would this cause the stutter,as the timing advances at high rpm .also when I hooked up the electric advance,cold start device on the top of the pump it didn't make any difference,it is activating ,but I read somewhere you can really hear the difference,iv got a compound gauge on a old truck ill put this on the filter and check out fuel pressure.the other question is does the factory lift pump get hot,may be I need to change it out!
 
What did you use to time it?
Cold advance, yeah. I went out and started my truck today with temperature of 95 degrees. I can here the difference of it advanced for the first minute or so- you should also.
What lift pump, the one for a ds4? hmm. Mine gets warm.
 
Thanks will
I timed the pump using the referance lines it starts really good cold,produces a bit off fuelly smoke for about a minute then its good,has a fair bit of combustion noise,wich it never had befor,,I'm thinking I might retard it a little as it isn't great at starting hot ,the pump might be worn ,don't know its history
 
Remember a tiny movement on the line is a lot. Do not move the pump with the engine running, it can break the pump. You have to snug one nut,my est start engine, shut off, then loosen nut and move pump, tighten nut, then restart. Torque all 3 nuts when happy with the clatter.
 
Yep sounds like a plan,am I right in thinking turn the pump body against the engine rotation to retard the timing?
I'm pretty sure timing is the issue the old girls only making about half the power that she used to have,
I'm back home in a week so I'll experiment and see what I come up with
Thanks for the advice regards chris
 
vintex said:
Yep sounds like a plan,am I right in thinking turn the pump body against the engine rotation to retard the timing?
I'm pretty sure timing is the issue the old girls only making about half the power that she used to have,
I'm back home in a week so I'll experiment and see what I come up with
Thanks for the advice regards chris
Click to expand...
Some 6.2 pumps even turned up won't put out that much fuel, so you may have one of those types of early 6.2 pumps. Even many of the later ones cranked still wouldn't do what a stock 6.5 pump would.
 
Its a thought ,my pump has a cam and arm for what I believe is the advance,I'm thinking this is early type.
Iv messed around with.the bosh rotary fuel pumps a bit and iv changed the rotor &head assemblys out for larger ones from bigger capacity engines to gain performance
Can this be done with DB2 or is it cheaper to by whole new pump,at the moment as long as I can get her to start better hot ill be a happy camper!!
 
Well guys got home the other day ,retarded the timing a little ,adjusted the throttle cable got every thing so it sounds about right .the only problem iv got is that my truck starts great around town on short runs,but if I take the two hour trip to work she's hard to start ,untill she's cooled down.
I'm presuming from what iv read on other threads the injector pump is coming to the end of its life,the only part that doesn't make sense to me is when I start the engine cold there's a fair bit of fuel smoke ,like it's over fuelling and the engine stutters a little untill it warms up a bit ( only about a minute),so I'm thinking its delivering plenty of fuel cold but not hot
What have I got for options?
Iv read about adding oil to the fuel ? Is there a down side to this ?
Any ideas???
 
2 stroke oil is a good idea, pour water on the IP head when warm, if it starts better the IP is worn.
 
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