ASE CERTS

[cointelpro]

im guessing its neither..

 

[CRX_B16B]

ASE practice test

 

[jamesA]

D

 

[ryanwolfe911]

Being an ASE master tech, (not bragging) I say "D". It sounds to me liek the turbocharger is malfunctioning. Thus causing the engine to run excessivley rich, producing the black smoke and lack of power. A turbocharger is very impoertant on a diesal that is equipped with one. It what is responsible for creating the very high combustion pressures that make a diesel a diesel. With the abnormally low compression, it runs very rich. Ever notice when a semi takes off from a start, that it pukes black smoke for a second or two? Thats because the turbo ahsn't spooled up yet, but when it does, the engine prouces the correct air/fuel ratio and runs at proper stoichometric efficiency. (for a diesel any way)

 

[ryanwolfe911]

here's one for you:


A 1994 Chevrolet S-10 Blazer with a VIN "W" multiport fuel injection system comes in with the check engine light on, a very hard brake pedal with little power assist and idling very poorly. ALso has a strong sulfur smell out of the exhaust. The problem could be:

Tech A says: EGR valve plugged up with carbon.

Tech B says: Leaking central fuel injector

Tech C says Both


Who is right?


I bet LOCO Honkey is the only one who get s this right

 

[Jeef]

I would say B since I know that is supposed to be a common problem on the W engines.

 

[Loco Honkey]

Originally posted by ryanwolfe911@Nov 25 2003, 09:33 PM
Being an ASE master tech, (not bragging) I say "D". It sounds to me liek the turbocharger is malfunctioning.

Being an ASE Master Tech, you should know that you're only allowed to pick between the four answers. Generally, if one or both of the causes they list could indeed create that situation, that is the answer. Yes, the turbocharger could be bad, as well as a clogged air filter, but Tech A and Tech B provide possible causes, therefore, the answer is not D.

The answer is C.

Tech A says the injectors are stuck open. If you read the question, it says the engine has a mechanical pump. Diesels with mechanical fuel pumps do not have injectors like a car, which are opened electronically. Rather, they have injectors that are opened by the fuel pressure which is typically 5000 PSI at idle. They can stick open, but this is rare.

Tech B says the fuel pump is faulty. Mechanical diesel pumps are essentially "fuel distributors" where they are responsible for ramping the fuel pressure and timing the injector spray with the RPM of the engine. A bad pump could cause a host of problems, one of which being excessive fueling.