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Discussion Starter #1
I have a 91' Chevy C1500 with a 305. I bought the truck for $200. The truck had been sitting for awhile and the previous owner did not know what was wrong with it. He said it ran but the ignition switch had to be replaced.

The items I replaced before i first started the engine for the first time:
Fuel pump/fuel filter/spark plugs/spark plug wires/distributor cap/rotor button/ignition coil/EGR Valve/TB Injector (both of them)/Coolant temperature sensor/throttle position sensor/MAP Sensor/Electronic Spark Control/Fuel Pressure regulator diaphragm/Ignition control module.


The truck is running now but i am having an issue with acceleration or acceleration under a load, constant speed while on the highway, slight tapping of the engine (think it comes from the passenger side of the engine). I have a strong gas odor and poor fuel economy. I found the #8 cylinder plug was not firing, it looked brand new as if it had never been installed in an engine and ran. #6 plug looked coated with a little oil but all other plugs looked perfectly normal. I have put 1500 miles on the truck before these problems just started showing up. The engine has Never backfired, but it seems like every time i put the truck in reverse it trys to cutoff. I am unable to set the timing correctly. The timing is 25 degrees advanced i believe in order for the engine to run enough to get to work and back. If i set the timing to Zero, the RPM is too low to run to stay running and the engine stumbles and will not accelerate. The truck will crack very easily but it will not stay running. The engine idles smoothly and i can rev the RPM at a normal rate but when i add any type of engine load the engine does not handle the load well and starts to struggle.
 

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Some of this sounds like the timing set, gears and chain, are worn out. That would be starts, runs and idles but will not take a load, wants a lot of base timing just to do that.

There may well be other problems but this one pops out first thing.

Bogie
 

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Be sure you are following the instructions for setting the timing on a throttle body engine. You Can not just put the timing light on it and turn the distributor.

John
 

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So when I attempted to set the timing I bypassed the ect like the book said and it would not run correctly. It actually ran way worst with the timing set to where it is suppose to be. Smh I guess I need to try and reset the timing or should I just replace the timing chain. Truck has 198,??? Miles on it. I am not sure when the timing chain was replaced last. What would you do?
 

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Set the timing where it's supposed to be with the 'timing' wire unhooked. Then watch the timiing mark and see if wanders while idling and when snapping the throttle. If it does, then the dizzy gear and/or timing set is worn out.

Before I did anything more than what you've done though I'd start with a compression check. You can throw all of the ignition and timing part sat it that you want, but none of them will make the compression come back. If the compression is good, then do as I described above. Then see where your vacuum is at idle.
 

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So when I did set the timing to where it is suppose to be, I did watch the mark and it moved very little. The engine would die just a little randomly and the timing would move and it would come back to normal idle speed And the timing would return to normal. With the timing set correctly engine rpm was extremely low but smooth. The dieing process was a very slow When I does try to die. When I accelerated the engine the timing moved a **** ton. It also accelerates decently with no load.
 

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198K miles..., yep time for rebuild, and very well could be weak timing chain.

In mean time can try a couple things to see if anything improves.

1. Fuel Gauge, make sure you not loosing pressure as you accelerate.
The ECU triggers the pump 3 to 8 sec, then shuts off, this just enough pressure to get the engine started. Once it starts it will build oil pressure and the oil pressure switch at back of block on drivers side, keeps the f-pump running. This is all in simplest terms, trying not to confuse, or get lost in weeds.

2. Take out module and have tested.
The module has both a high and low side to it. The low side will start and idle. The high side will handle load and acceleration. High side failure will give you exactly what you are experiencing.

Possible R&R parts you might need

1. F-Pump Relay
2. Oil Pressure Switch
3. New Ignition Module, ...get the $40.00 (ish) unit, the cheaper ones are usually poor or at least questionable quality. Stay away from the Accel Module if available, the older one were good, newer ones, not so much. The AirTex, AC Delco, Echlin, Standard are better, but more money.


3. Cams
Yours should be roller cam, TBI, 627 Block which is a good engine, but at 198K time for replacement. The 82 to 87 flat tappet cams prior to roller cams were soft. I replaced "many" at the dealership back then. Figure out how you best want use the truck and go from there.

4. Other obvious things is compression.
With 198K miles, low compression due to wear, will also cause loss of power and poor drivabilty.
 
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