QuestionHarry, can you tell me if the lift pump referenced in your answer below ( I copied your answer to another person's question so you would know what I was talking about)is included in the extended warranty (11 years or 120,000 miles) on these diesel engines? Seems like this whole configuration is an incredibily poor design. Also, I see where the lift pump on the Cummins was recently recalled (see link). What do you think about this? Can you see why these situations are different? Why not recall the GM diesel? Thanks, Johnb
link to Cummins recall:
http://www.theautochannel.com/news/2005/09/07/142309.html
Your Answer to a previous email:
Your problem is likely with the Oil Pressure Switch (OPS).
GM designed these engines with electric fuel transfer (lift) pumps and needed to ensure that the fuel supply was shut-off in the event of low engine oil pressure or an accident.
The trouble is that the lift pump draws about four Amps and the OPS is rated for about one Amp. Over time, the OPS contacts go bad and this causes the lift pump to shut off and starve the injection pump for fuel.
From diesel forums (my diesels have electric lift pumps but no OPS), I believe that the test is to open the fuel filter bleed valve with the engine idling. If fuel does not flow out in a solid stream, then either the OPS or electric lift pump is bad. You can run +12 Volts to the pump directly and retest. If the fuel flows properly, the OPS is bad.
The OPS is located on the back of the engine, near the driver's side cylinder head. I understand that a special socket is recommended for removal and replacement of the OPS.
AnswerJohn,
GM did not warranty the lift pumps. They warrantied the injection pumps and injection pump electronics for 11 years or 120,000 miles. Sadly, it is often the malfunctioning OPS that contributes to the demise of the injection pump and/or electronics due to the lack of excess fuel to carry away heat (diesels return excess fuel to their tanks for this purpose).
Yes, the GM OPS was not well designed (nor was the electronic control system for the injection pump). But, accountants run GM and a nickel saved per vehicle is something they salivate over.
Dodge/Cummins, who both should know better, also goofed on the lift pump installation on the newer 5.9s. Pumps push liquid better than they suck and an elevation change makes life very hard for a suction pump. Cummins may or may not be responsible for the problem. Dodge may have come up with it on their own.
I have electric lift pumps on my early 6.2s. But, they are back by the fuel tanks and they do not have an OPS controlling their power. They work very well and my diesels start instantly hot or cold (albeit after one cycle of my manually-controlled glow plugs).
