Difficulty timing a 1995 Chevy 454ci

OutofTime wrote:
Updates

Got the new injectors in and it is running better. Spray pattern looks better too.

Finally got down to checking the time under computer advance after setting it to 4 BTDC and I found today its advancing 20 degrees. I think that is why it's popping when under computer advance. Is 20 degrees normal at idle? A possible X factor would be that there really isn't much water in the cooling system at the moment so the ECT probably isn't reading as closely as it should.

After rebuilding the distributor on my 1994 P-30 chassis 454 TBI at idle with the wire connected it will idle at 16. Idle RPM 800.

I use a bluetooth ALDL phone app and the following...

http://www.1320electronics.com/12pin_ALDL_BT_MK2.html

I can check on this today. I have checked for vacuum leaks and did replace a few rotted out lines. I've also redone all the gaskets on the tbi, including the base plate gasket.

Does the timing return to 4 degrees when you disconnect the tan wire?
What RPM is the engine running at?
20 degrees sounds about right with tan wire connected.
I do not remember after 6 pages whether you checked for vacuum leak.

Updates

Got the new injectors in and it is running better. Spray pattern looks better too.

Finally got down to checking the time under computer advance after setting it to 4 BTDC and I found today its advancing 20 degrees. I think that is why it's popping when under computer advance. Is 20 degrees normal at idle? A possible X factor would be that there really isn't much water in the cooling system at the moment so the ECT probably isn't reading as closely as it should.

I haven't had the tooling to check yet. I think I have a fuel pressure gauge somewhere but I need to find it again. I wasn't thinking lean because of the black smoke belching out but with much of that getting cleaned up by the TPS reset, now I'm wondering... First thing to sort maybe this weekend is the cooling system so I can run the engine longer to do more testing.

What was the fuel pressure at?

94-95 years was 26-32psi (preferably higher than 26psi)

Indeed. At one point I did have the timing at TDC and the popping went away so.... but the rev issue was still there. That was pre messing with the TPS.

I can try to set it to 0 TDC now that it will rev and see what happens. I hope this weekend I'll have time to at least pull the water pump, but with 30 year old rusty bolts, that's a tall order.

At this point I can keep plugging away at it and fix it bit by bit. This also informs well for me as my housing plans include purchasing an RV eventually so that I can remove my current house and place a new one while still living on the property. I hope I don't wind up purchasing something as old as a '95 but you never know what your budget may wind up being.

I commend you on two fronts. One, it is becoming a rarer breed to try to fix things as opposed to calling in the cavalry. And your labor of love of doing it for a relative takes that to a new level. Second, I commend you on the way you handle input on the interweb. Not everyone is open to input despite asking for it. Good job on both fronts.

Short of pulling the timing chain cover and looking at the marks, there is one quick thing you could do just for giggles. It is obvious that the engine is firing early before the intake valve closes. Would you be willing to time the distributor (with the ECM connector removed) to the big indent in the timing marks instead of the mark you read to be 4? I don’t think that will make that much difference, but it’s worth a data point to see what happens when you reduce the advance on the initial timing. I have seen some reference material that indicates the big notch is the one to use. Keeping in mind your engine and the engine in the reference sources may be slightly different. If it does reduce the popping and allows the engine to rev more freely then you will at least know you are moving in the right direction.

I understand about the parts cannon logic, my perspective was to reduce the confounding factors in the problem solving.

Yeah, that’s a bit far for a play date, since we leave in 2 weeks for a 6 month trip to Alaska. Better stay here and focus on HER list to keep the peace.

So after messing with the TPS, it will rev with advance connected. Still pops and such, but it will now rev.

Let also expand on what I mean by a slipped balancer. I have a '94 Mazda B3000 that when I first brought it back to life I could not get it to start when I set the balancer to 10 BTDC, which is Ford spec for a Vulcan 3.0 engine. Made sure I was on compression stroke, etc. When I finally timed it manually by putting something in the number 1 cylinder and checking tdc, then pointing the button at tower 1 on the hat, it ran. Once running I put a timing light on it and saw the balancer marks were not lining up.

What happened is the glue that holds the rubber ring of the balancer to the metal core had given up so the rubber ring was beginning to slid somewhat around the core. That is what I mean by "slipped". Failure in that way would not shear the woodruff key in the metal core of the balancer.

As to the timing marks next to the balancer, they are intact enough that I can read the numbers, so I am timing to the correct 4 mark. 4 is listed twice, but the BTDC marks are more numerous than ATDC so I've got the right one. It's the last peak before the big groove that is TDC.

I agree timing still could have jumped a tooth at the chain due to age and slop and that does need to be looked at. That will probably happen when I service the water pump since I'll have access at that time.

I also agree that I need to pop the valve covers and make sure I don't have a tight/loose valve(s) that are causing issues

Progress is being made. After getting it timed again at 4 BTDC and then doing some testing, I'm pretty sure the balancer has NOT slipped and that something else is causing the running issues. The PO mentioned he replaced the fuel pump. It very well could be he put the wrong one in. He wasn't very mechanically inclined and could have put a lower flow pump in that doesn't match up with the increased psi that is required for the 1994-1995 TBI setups. I need to check fuel pressures to verify that. If it's really been running lean all this time with a dodgy TPS it could have caused the issues I've seen.

I have a vacuum gauge on the way that should tell me quite a bit about the engine's health now that I have the engine running consistently

As far as loading the parts cannon goes, I have. This RV is not for me and will be a home for a relative for what I think will be a very long time given the relative's situation. For that reason I am more comfortable to load the cannon and go ahead and replace the 30 year old parts with OEM new parts as needed to make sure the service life of this engine will continue on for quite some time. If this was a project vehicle of mine I would be quite a bit more stingy.

You raise some excellent points, and I most certainly don't take offense. This engine platform is new to me, which is why I wound up posting here to tap the brain trust so I can learn more.

As to your offer of a consult, that would be a road trip for you I think. I'm south of the Capital and I see that Inverness is a bit north of Tampa. I'm totally open to a video call of some sort to swap knowledge though.

I just have to say there is no ill intent on my part. But I am pretty sure this is a different read for the people reading than it is for the poster.

When you hear hoofbeats, think horses not zebras. All signs point to a timing issue. You can continue to throw money at it, but until the timing is addressed, it is just a frustrating exercise. Continuing to throw parts at it only increases the odds of some issue arising with the new parts to compound the problem.

Second. Insanity is doing the same thing over and over, but expecting a different outcome the next time. Point being, you set the timing to 4 BTDC with the timing connector disconnected, and it sort of runs. Then you connect the timing connector, and it falls flat. Meaning there could be something in your application of the setup routine that is causing this, and therefore the symptom keeps repeating itself.

It is popping back through the TBI. Meaning the timing is too early for the position of the valves.

I can think of two possibilities that would explain this.

One, is the correct mark for 4BTDC being used on the harmonic when you set the original timing? There are four marks on that harmonic. Are you using the big indented mark or a mark 3 notches over from that one? This also could be the whole basis of the distributor being off. Are you 100% percent certain the piston is at TCD when putting the distributor in, or are you using that timing mark as the indicator that the engine is at TDC. After all you keep mentioning the harmonic slipping on the crank. That simply does not happen with shearing the key.

Second, the engine has jumped time and the valves are no longer in time with the piston. This very much will cause poor ignition and popping because the valve is opened when the engine fires. As you mentioned earlier, pull the valve cover and watch the valve train actuation as the engine is barred over. Also, a compression test would tell you somewhat if the engine were out of time.

I am not criticizing you, please don’t read it that way. There is benefit in having a third party looking over your shoulder to identify what may be going on.

I think you are in Florida from your profile. Where? If you are close, and I live in Inverness, would you be open to on site help?