OutofTime wrote:



I verified the harmonic balancer is good and has not slipped. I posted it earlier in the thread but I took a 1/4 extension and slipped it into the spark plug hole on the number 5 cylinder, then rotated the engine until the extension was jammed in place by the piston coming up. I then checked the balancer and found it approaching 4 degrees BTDC, so the balancer is safe to use as a timing mark. That's how I got it running again. I have adjusted the timing by ear by turning the dizzy to where it will crank when you just bump the key and it will start hot or cold, which is a big improvement.

However, it's still running rough and pig-rich. That's why I want to verify all the sensors and get a timing light on it to really get the timing as precise as I can.

Based on how it runs it may be down a cylinder so I still need to verify that as well. When I changed out the spark plugs the plug that came out of cylinder 7 was pretty fouled with oil, so the oil control ring on that cylinder is pretty worn out. That one might be down.

It also looks like at some point in the RV's life the catalytic converter was removed. The O2 sensor is still there, but I don't see the cat. That could also be a piece of the lovely smell problem coming from the exhaust.

I haven't done my audit of electrical grounds yet, was focused on getting it running. I agree that bad grounds cause strange behavior. I had an Outback that was a crusty northern car and it ate headlight bulbs and shifted really rough until I cleaned all the grounds. The battery cables can probably stand to be replaced, but I'll get there.

I also need to go through the general wiring as the electric fan on the radiator doesn't seem to be running once the engine gets to temp and it sounds like the mechanical fan needs a new clutch. I also haven't seen the tiny engine bay cooling fans kick on either. Plenty of work to do in order to get this one sorted.

Does anyone know what color spring is needed for the 94-95 FPR? I can find plenty of kits with springs that claim they work for 94-95, but they also claim to work all the way back into the 80's model years so I don't know how that is possible with the change in fuel pressure in 94-95.

As long as you guys are willing to offer wisdom, I'll offer updates. This is my first GMC engine and chassis so much for me to learn here.

enblethen wrote:

What spring kit did you get and what color springs?
here is information for one kit:
This kit comes with 3 sets of advance springs to allow you to adjust the rate of spark advance from quick (Brown), to super-quick (Silver), to ultra-quick (copper).
In this kit, I would use none. I remember mine as being green.

OutofTime wrote:

I have updates. Today I worked with my brother and we got the base timing set to 4 degrees BTDC using a timing light. Once computer advance turned on it advance to around 16 BTDC at idle. It seems to be idling much better and will idle around 850rpm or so when warmed up and on closed loop running.

However, it's still running a bit rich and still stumbling and falling on its face when revved. I pulled the IAC, cleaned it and the bore it sits in and checked for operation. I did see the pentile tip move in the throttle body when I turned the key to the run position.

I checked the voltage on the TPS and at full stop it read .568V, which is within spec I believe.

At this point I'm thinking my next move to fix this rich running is to replace the FPR.

OutofTime wrote:

More updates. Put in a new ECT and it runs the same, if not a little worse before getting to closed loop. I think the new ECT is defective as at 72F it was clocking about 2.55k Ohms, which according to the chart provided is not correct. Are there any brands of ECT that are better than others?

Also, I'm thinking that the FPR is the cause in part for the black smoke and almost stalling when you rev the engine. I have a TBI rebuild kit for a 5.7 that has the right gaskets and I have a spring on the way from shop link provided, so that should hopefully correct the FPR.

Also getting plenty of backfires when putting the engine under load.

Thoughts?

OutofTime wrote:

Moar updates. Yesterday I changed out the thermostat and installed a new ECT that clocked much closer to chart when ohm'd. Existing thermostat was a 195F which is good, but from what I was seeing it was quite old. I also inspected the wire harness ground on the water neck stud... it was not so great. Cleaned it up and all the metal in that particular stack for a solid electrical connection. This morning I replaced the blown out PCV valve, replaced a failing vacuum line from the Evap valve to the throttle body and fixed the cracked boots on the PCV valve vacuum line. I also replaced a fuel filter of unknown age with a new Wix one.

Before I test fire it again I intend today to clean the ground strap from the rear of the driver's head to frame and wherever the negative battery terminal is grounded to.

I'm hoping after all this work I see some improvement. We'll find out this afternoon.