Electrical or fuel problem???

[Dave Masotti]

:confused: I have a 1994 3500 HD Chevy, 6.5 turbo. Problem is real loud rattle and knocks till temp is up to around 200. After that it sounds quiet and normal. I feel it's a sensor of some type but have no clue where to start. It's not a mechanical knock, sounds like fuel to me. I am inclined to think it's electrical and any draw at all electrically messes with the guages. Also if the lights are on, or my foot is on the brake it won't shut off. Take your foot off the brake or shut the lights off and it shuts right off. HELP... this is driving me crazy..Engine itself runs fine. no skips or smoke at all. Thanks.

[rjwest]

Suggest fixing electrical problem first.

Sounds like there are 2 feed wires shorted together.
Or bad ground...

Check for grounds first. VERY critical to electronic controls.

[Dave Masotti]

Thanks RJ...I've checked all of the grounds and they are fine. Even replaced one battery that had a questionable terminal.the pump timing marks are set about 3/16 to the passenger side. Starts perfect. When i pulled the codes it showed 15 different codes, most i believe are redundant. SES light will only come on if you do a hard accel run.When you restart the engine, no SES. Even hot the noise comes and goes. Sometimes quiet as a gas job and sometimes sounds like a 30 degree temp start. As far as 2 feeds being shorted it will take forever to sort that, ecspecailly not knowing if it would be under the hood or under dash. Most prominent codes were 35,62, 27. I could be wrong but i think one of these is really the problem and is setting the other codes. Am I making sence? Is it possible that it's the pushrod for the vacuum pump? I've heasrd this on SBC's very often on the fuel pumps. Truck has 80,000 miles on it.

[rjwest]

I'l try to do some thinkin,
May try to listen ( hard to do with eng running )
and feel the fuel shut of solenoid
while someone repeats shut off problem
IE shut off eng with Brake depressed and normal.

To see if solenoid is really affected and by how much. Would expect solenoid is not closing or closing partialy,


If you need a " test" fule solenoid, I could mail
you a loner.

Last thought for now. Ign sw, wiggle it
when " shut off problem occurs, I think there have been problems with ign sw's....

[rjwest]

Code 27 Acel Pedal 2 circuit low.
Thats the sender attached to the throttle pedal

Code 35 Inj pulse width error , responce to short ( cab be bad pump )

Code 62 Turbo Boost Sensor circuit Low.
Sensor on top of maniofold

I do not see any logical connection to above codes,
other than electrical gremlins...

The " No Shut off" is a real mystery ( at least to me ).

I do not know if shuting off the fuel solenoid is the only commanded " Eng Shut Off '

If it is , than there is electrical power getting
back to solenoid with ign in off position.

IE,Headlight/brake power shorted to Ign run circuit , Do you have any " ADD ON's " Trailer wiring,
etc. Will it keep running with only running lights on?

As for the engine running rough at times,
May or may not be related to " No shut off " problem.

You will probably get more help after weekend,
Hopefully from someone who has a 94-95 series truck.
Good luck....

[Hubert]

check that electricity is getting cut off with the switch to the controls.
Its those common wire circuits that are tough to figure out. My experience:

I had a no shut off problem turned out to be trailer connector back feeding circuits

I had installed a reciever type hitch a few weekends before the problems started. The previous owner had a trailer brake controller. While I was installing the new hitch I evidently twisted/yanked/moved the trailering harness hard enough to pull loose inside a thicker guage hot wire going to the trailer brake pin. This loose hot wire would make a connection thru the ground/reverse lights to power various controls.

On my 97 with the key on run power runs from ignition switch to node S109 then to various circuits ( the fuel solenoid, electronic control module and others) From node S109 voltage is also supplied to the backup lights circuit. IE to the reverse switch on transmission then back to the bulbs. Backup lights are grounded at the back of the truck and power comes from S109 when the ignition is on. The loop is closed and backup light come on when transmission is in reverse. In my case when I turned the key off while in reverse voltage from the loose wire in the trailering harness was traveling back up to node S109 keeping power to the various engine controls even though the key was off.