A reader tells about blown fuel pump fuses and a surging problem on his 94 Blazer
Hi Bob! Great web page. I have made a few unusual repairs on my Brothers 94 S-10 Blazer and I thought I would pass them along. The first problem: Blown fuel pump fuse. The fuse would blow after about 30 seconds of run time. I checked the wiring and it was fine back to the pump. I replaced the pump and had the same problem. So I pulled the pump and inspected the sending unit assembly that the pump is attached to and found that the plastic connector that the wires pass through was badly burnt. I replaced the assembly and the problem was fixed. Whenever replacing the in tank pump, check the sending unit. This also solved an intermittent no start after the vehicle was hot. This only happened on very hot days and by adding 5 gallons of cool fuel the truck would start. It would also restart after it sat for a few hours. I think when the tank heated up the connector lost contact.
The second problem: Surge at idle followed by a stall and no start. The problem started while driving down the highway. The truck started missing and running rough. When I checked it out, the plug wires were arcing at the distributer cap. The truck was due for a tune-up so I installed a new cap, rotor, wires, module, and plugs. This fixed the arcing problem but not the surging/stall. I checked the fuel pressure and it was within spec but on the low side. I put my scanner on and found no codes and erratic readings from the sensors due to the surge. I eliminated the TPS, MAP, IAC, EGR and O2 sensors by individual testing. The engine backfired through through intake so I suspected a lean condition. I rechecked the fuel pressure and found that when I snapped the throttle, the pressure dropped from 55 to 41psi. (spec is 54-64 psi). I then pinched of the return line and had 65 psi. The fuel pump was good. It was the CPI unit which houses the fuel pressure regulator that was bad. The unit was less than 2 years old, and very expensive ($360) so I was surprised to find that it was bad. The replacement took about 1.5 hours and was very easy. You pull the upper plenum and it is right there, no special tools required. The truck is now running great. I hope this info is useful to someone and not to wordy. I am an automotive engineer working for the Minnesota Pollution Control Agency on mobile sources of pollution. I work on cars as a hobby and have had a lot of success by using the internet and other sources of info to be properly informed and make safe effective repairs.
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