Biomechanics

no biodiesel, there's your problem

By Dan Freeman

More in the Fall 2009 issue

I just got back from working a biodiesel booth at the Association of Diesel Specialists (ADS) International convention in Washington, DC. These are the folks who rebuild fuel injectors, injection pumps and turbos.
To my surprise, we got a great reception. Many of the shop owners were biodiesel friendly, made their own biodiesel or raced their personal trucks with it!
Since I had all these knowledgeable and experienced diesel specialists flying in from all over the world asking me questions, I thought I should ask them some questions about pump and injector failure.
The general consensus was that the main cause of injection pump (IP) failure was lack of fuel. 
Read: CLOGGED FILTERS!!!!
(And, of course, leaks caused by ultra low sulfur diesel (ULSD)). 
Fuel is what lubricates the IP. No fuel, no lube, no go, things go boom! 
The first thing that happens to a Volkswagen TDI IP when it is denied fuel is that the suction pump or lift pump actually begins to cavitate. The pump has to suck so hard that the vacuum created begins to vaporize the fuel, causing little explosions inside the pump. Then the lift pump goes and pukes it guts into the rest of the IP, causing damage and mayhem.
"Why, Why, Why!" you exclaim.
Because you did not use protection, and thus exposed your pump to dirty fuel.
Shame!
An injection pump is a terrible thing to waste. 
So, is your IP well fed? Are your fuel filters restricted? Is your tank infected with the crud?  Let take a look-see.
In diagnosing a TDI, the first thing I do is go for a test drive. Is the car quick and perky?
Then I look for air in the fuel lines and test for fuel restriction after the fuel filter with a big vacuum pump that looks like a garden sprayer. One stroke of the pump should yield generous fuel.
If it doesn't, the filter or fuel system up stream may be restricted.
Next, I check up stream just before the filter, and then at the fuel tank itself, until I find the source of the restriction.
On a TDI, it could be the filter, fuel line check valves and/ or the in-tank fuel pickup. On the Pump Deuse models it could be the in-tank lift pump.
TDIs have their fuel pickup under the back seat. It's easy to remove and look into the fuel tank.
CLEAN OUT YOUR TANK! What the hell is in there? Is that OK? NO! Anything other than fuel has to go!
It's not that hard. Raise the driver's side of the car a little and pump out the fuel. Then reach into the tank and carefully wipe it out.
At Dr. Dan's, we sometimes even update the fuel pickup with a cold weather version that seems to help improve fuel flow.
Flush out the fuel lines. Bleed the fuel system to purge any air. 
Now how does it run? Happy? Perky? O.K. Good job!
Keep it clean, use protection, do good work and spread good knowledge.

Dr. Dan is a mechanic with 30 years of alternative fuels experience. He runs Seattle-based Dr. Dan's Alternative Fuelwerks, and does biodiesel training classes and consulting. Visit him online: drdansbiodiesel.com

Dr. Dan is a mechanic with 30 years of alternative fuels experience. He runs Seattle-based Dr. Dan’s Alternative Fuelwerks, and does biodiesel training classes and consulting. Visit him online: drdansbiodiesel.com