Hi all

this is my first posting....I live in nor cal. I own one 85 suburban k2500 6.2l 3/4 ton 4x4.....I have run petro/bio mixes...and straight bio-diesel...

so here are my issues...

1. It seams that the stock lift pump(fuel pump) cannot handle the bio diesel...at least this is my thoughts...I recently had to change the pump due to leakage after one year of use..(which by the way drasticly improved my cold starts) now after a month of running a mix of bio/petro without any real (different)cold start issues. I have begun to run straight bio diesel over the last 4-5 days and the last 3 days the truck seams to be having a much harder time cold starting...it takes at least twice as long to start...and getting longer...

I have replaced all the fuel lines with viton tubing except the lines that come off the metal lines to the gas tank...which will happen soon.. also have added a raycor fuel/water separator

I have replaced the whole glow plug system including wiring a momentary switch into the stock system to allow for manual glow plug activation..
because the truck once up to temp. and sitting for more then 20 minutes it will not start due to themo-sensor in glow plug system telling it not to activate..plus i'm sure there are still air leaks in the system...

so my questions are this...

1.does anyone know if the stock mechanical fuel pump or the fuel sending unit in the fuel tank has parts that bio diesel will destroy??

2.do i bypass the stock fuel pump and add a new electric pump bio resistant...and where due i find one of these handy units...or should i just add a second elect. pump?

3. where can i find injector pump seals made of viton...they were replaced about 2 years ago(before i owned the truck) but with nitrile seals??

4. can I get a referral for a (trustworthy/not too expensive)mechanic in the s.f/oakland bay area...I have to have the timing chain replace very soon...plus needs steering/suspension work??

there is a section on biodiesel you may get answers there. if i knew i would tell you.

sitting for more then 20 minutes it will not start due to themo-sensor in glow plug system telling it not to activate..plus i'm sure there are still air leaks in the system...


Only 20 minutes shouldn't be a problem. I can wait for an hour or maybe more and start without using the glow plugs --- it takes a bit more cranking, so I glow when the coolant temperature is low to make it easier on the starter. If it's 180 or above, glowing doesn't make a noticeable difference; it takes about 3 seconds of cranking when it's down to 140 or so.

Do you have the extra filter installed on the sucking side of the lift pump?


1.does anyone know if the stock mechanical fuel pump or the fuel sending unit in the fuel tank has parts that bio diesel will destroy??


The mechanical lift pump is a diaphragm pump. The diaphragm is probably made of some type of rubber. You could open one to see what's inside.


2.do i bypass the stock fuel pump and add a new electric pump bio resistant...and where due i find one of these handy units...or should i just add a second elect. pump?


If you use two pumps, either in series or in parallel, chances are that the pumps interfere with each other. It's a lot easier to use only one pump.

If you switch to an electrical pump, remove the mechanical pump, take out the pushrod and close the hole in the block with a blocking plate. The plates for Chevy gassers from autozone fit.

I don't know if they are biodiesel resistant, but you can check out the Holley Red and Blue pumps --- preferably the Blue because it allows you to optimize the fuel pressure. They are rotary vane pumps which probably don't have rubber parts in the pumping assembly itself --- there might be a rubber seal that seals the pump assembly from the motor, though. But afair you can get rebuild kits for them; if the kit contains a seal to seal off the motor, you could replace that with a resistant seal.


4. can I get a referral for a (trustworthy/not too expensive)mechanic in the s.f/oakland bay area...I have to have the timing chain replace very soon...plus needs steering/suspension work??

You could do a better job than someone you pay by doing it yourself, and it would be much cheaper. When going so far as to replace the timing chain, that would be the time to install a new water pump, a new balancer, eventually a new crankshaft pulley --- all those have to be removed anyway. You could get a gearset instead of a new chain (and still save money doing it yourself).

If you pay someone, they will want to make money on the parts, too --- like two times of what the parts cost. A remanufactured water pump costs about $30, a new one about $60; a new balancer costs $80, a timing cover gasket set costs $13, a new three-groove rubber pulley (dealer only part) costs $325. Without the pulley, you save already $150 on the parts, plus what you save on the timing chain.

And doing it yourself is the only way to know that it's done the right way.

i missed the part about the glow plug inhibitor switch . it will be a two pronged plug, just wire acrossed it. gms fix was a plug with a full time closed switch. same thing as wiring around it. all four of ours are wired around.

thnx for your time friends....

I have already purchased from rock auto...if you know of a cheaper spot to buy from would love a redirect....

timing gear set + half moon keys(Santa Barbra gmc), water pump(stock pump), and gasket set + oil seal... Do you really think replacing the balancer is necessary?? and why...I would almost think it might throw some things off...but could b wrong of course...

I have a mechanical background but is not one of my skills that I practice not to mention I don't have an extensive tools set anymore... I don't want to embarrass myself by telling you all how long it took to replace the last fuel pump...dam gaskets suck...

so I am looking for someone who actually does it often...

Hi welcom to the forum :D

Your problem look a air leek in the lines connection more than any other thing if your IP war rebuild 2 years ago nitrile seal is in and they are ok with bio-diesel .

first replace yuour fuel filter = the bio is a cleaning agent and may claug your fiter soon. at the same time install a clear line to see the air going in the fuel lines , you can install it on your return line on the top of your IP or at the filter output.

If you have to replace your IP here is a trick;)remove your oil tube and

http://i68.photobucket.com/albums/i29/tigman_photos/diesel/10-04-07_2155.jpg

It save you time, lot of time:muahaha:

Ed

Do you really think replacing the balancer is necessary??

Yes, really.

If the balancer is old, the rubber has become hard so that it cannot exactly do its job anymore. Eventually the rubber has started to come out. A bad balancer can lead to a broken crankshaft, so changing it is cheap insurance.

When I replaced mine, it made quite a difference, the engine was running a lot smoother. A fluidampr would be even better, but the price kept me away --- maybe I'll get one some time, they are easy to change ...

Since you already got a timing gear set, get at least a new balancer (if yours is 10 years old or older), if not a fluiddampr ...

And check the crankshaft pulley. If you have the rubber version, there's a good chance that it is worn out --- mine was. If you need to replace it, you might be able to find someone here who can sell you a spare ... Just make sure you get the right version, like three grooves if you have A/C, two grooves if not. The two and three groove pulleys are interchangeable, though, i. e. two groove will fit but not have a groove for the A/C compressor belt --- and since a two groove belt fits for that, a three groove pulley will also fit if you don't have A/C. You could then use the unused groove to run a second alternator ...