OT - Setting Timing on a TBI 350 Engine

[Fasttrack]

So I finally got the engine replaced in my truck but I'm having trouble getting it to run :(

I think I'm just fighting with the computer. I've got the ETS wire unplugged (I think) and when I can get it to start and idle well. But if I goose the throttle then it dies (understandable since I don't have any ignition advance without the ETS plugged in). When I try to restart the engine, it runs rough. Eventually, it just won't start unless I let it cool or dicker around with the timing again.

I'm going to buy a proper timing light tomorrow, but I was wondering if anyone had any advice for me.

[wrenchbender]

been awhile since i worked on a tbi. engine.
as memory serves me and it is a little fuzzy.
there is a sensor wire on the distributor that needs to be unplugged to allow the thing to be timed if you do not you can turn the dist. all the way around and it will maintain the timing as is. there is more to the procedure but thats the meat and potatoes of it.

[Fasttrack]

been awhile since i worked on a tbi. engine.
as memory serves me and it is a little fuzzy.
there is a sensor wire on the distributor that needs to be unplugged to allow the thing to be timed if you do not you can turn the dist. all the way around and it will maintain the timing as is. there is more to the procedure but thats the meat and potatoes of it.

I've got that wire unplugged but I'm still having trouble. My '77 Chevy was much easier :o

[Bguns]

Why goose engine while advance is unplugged...???? Probably loading up O2 and other sensors to boot...

Just unplug, set timing, tighten down distributor, replug, restart, and then goose away,,,

Just set one last month after a new long block install...

Computers change the old ways of playing with engines...

[saltmine]

That's about it, Wrenchbender. unplug the wire, set the timing, and plug it back in.

No, you can't rely on the "MK-1 eyeball" or the "sounds right" or even a vacuum gage. With electronic spark control, it has to be set "dead nuts" with a timing light.

You're lucky, in a way. Later model "R" engines with CMFI, don't even have timing marks. You have to set the distributor static, fire it up, and do a "crank learn" with the help of a scan tool. What's even worse is the fact that the "R" engines have plastic distributor housings, and no provision to advance or retard the timing...It goes in one way, and that's it.

Many a distributor has been broken by somebody trying to "set the timing".

[Rob Garner]

Edit: Damn I am a slow typer. There was only one reply when I started.


So I finally got the engine replaced in my truck but I'm having trouble getting it to run :(

I think I'm just fighting with the computer. I've got the ETS wire unplugged (I think) and when I can get it to start and idle well. But if I goose the throttle then it dies (understandable since I don't have any ignition advance without the ETS plugged in). When I try to restart the engine, it runs rough. Eventually, it just won't start unless I let it cool or dicker around with the timing again.

I'm going to buy a proper timing light tomorrow, but I was wondering if anyone had any advice for me.

Huh... had to deal with a very similar problem myself today.

The wire you need should be under and to the right of the brake booster when looking from the front. It should be a single tan wire with a black stripe.

http://i159.photobucket.com/albums/t150/robg_010/S6303396Medium.jpg

When the dist. was put in, did you have cyl. #1 at TDC on the compression stroke?

Does the rotor point to the #1 post on the cap at TDC? Maybe off one tooth?

http://i159.photobucket.com/albums/t150/robg_010/firingorder.jpg

Is the dist. good? This was my problem. The pickup coil was failing thus causing the truck to stall when stopping.

Double check that you have the plug wires on the cap going in the right direction. Going CLOCKWISE it's 18436572. :rolleyes: (Brainfart don't ask) only took an hour to figure out my screw up.

Are all of the sensors known to be good?

[saltmine]

On most S-10's it's under the heater box, inside the cab, on the passenger side. Color code is the same, connector is different....Does the same thing...."EST Bypass"

That's OK, Rob. When I retired four years ago, I could only type with two fingers...Now I'm up to seven.

[Fasttrack]

Why goose engine while advance is unplugged...???? Probably loading up O2 and other sensors to boot...

Computers change the old ways of playing with engines...


Because I had a brainfart. ;)

I'm headed out to buy a proper timing light this evening after work. Then I'll set the timing correctly and see where I end up. I'm really hoping that is all there is to it. The distributor is new as of 1 year ago and everything was working great (except for burning 5 qts every 3 thousand miles) when I swapped them over to the new engine.

Thanks Rob for the pictures. I found mine located on the firewall behind the distributor and slightly towards the passenger side. Same connector and same colored wire going to the dist - I assume it was the correct one to unplug.

Thanks guys!

[Fasttrack]

Alright I need help. I'm about ready to throw a hammer through the windshield.

With the ETS wire disconnected, I set the timing to 2* BTDC. It was nice and solid and it idled great. I shut it off and plugged in the ETS and fired it up. It started up with a little cough but ran ok at idle for about 1.5 minutes and then it started bogging down and coughing like the timing was way retarded. Then it would rev up and even out. This pattern continued once or twice before it finally died.

Now it won't start. It will fire and cough and sputter and then die. Doesn't matter whether the ETS is connected or not.

Also, I noticed that the aftermarket tachometer (which had previously been working) is acting crazy. Right when the engine starts running crazy, the tach indicates 1800 rpm when it sounds more like 600-700. This tach plugs into the distributor - it's not an inductive one.

SO ... bad ECM? Bad temperature sensor? Bad mechanic?

[saltmine]

Sounds like you might have a bad ground, or one not hooked up.

Could be an ignition module going bad, also, but remember, with the EST connected, the timing will jump around, all over the place, as the ECM runs the timing.

Of course, when you disconnect the EST plug, the ECM goes into a base mapping mode, even older computers do it. By plugging it back in, you go back to full computer control. One thing you need to do is find out what's going on in there. Scanning it would help immensely..especially if the guy holding the scan tool knew what he was looking at (definitely not the guy at VatoZone)
Being TBI, fuel pressure makes them do all sorts of weird things. 13psi is the magic number for TBI engines, no more, no less. Yes, use a pressure gauge, don't guess.

You could also be experiencing an ignition coil failure...happens.

Word of advice: When you're satisfied you tried everything, take it to a professional. Now, hold on, before you start ranting...yes, it costs money to have a well trained professional look at it, but if he's good, he can find things it would take you a month to locate and correct...so you're actually money ahead, at this point.

I should know. I was the trained professional people used to bring their cars & trucks to when they were at wits end. Diagnosing car problems over the internet is like trying to teach somebody how to f**k the first time, when they have no experience.

Diagnosing car problems is something like jumping into a volcano....You'd have to be there, to get the whole picture.

[Fasttrack]

Sounds like you might have a bad ground, or one not hooked up.

Could be an ignition module going bad, also, but remember, with the EST connected, the timing will jump around, all over the place, as the ECM runs the timing.

Of course, when you disconnect the EST plug, the ECM goes into a base mapping mode, even older computers do it. By plugging it back in, you go back to full computer control. One thing you need to do is find out what's going on in there. Scanning it would help immensely..especially if the guy holding the scan tool knew what he was looking at (definitely not the guy at VatoZone)
Being TBI, fuel pressure makes them do all sorts of weird things. 13psi is the magic number for TBI engines, no more, no less. Yes, use a pressure gauge, don't guess.

You could also be experiencing an ignition coil failure...happens.

Word of advice: When you're satisfied you tried everything, take it to a professional. Now, hold on, before you start ranting...yes, it costs money to have a well trained professional look at it, but if he's good, he can find things it would take you a month to locate and correct...so you're actually money ahead, at this point.

I should know. I was the trained professional people used to bring their cars & trucks to when they were at wits end. Diagnosing car problems over the internet is like trying to teach somebody how to f**k the first time, when they have no experience.

Diagnosing car problems is something like jumping into a volcano....You'd have to be there, to get the whole picture.


Thanks Saltmine. I already considered taking it to a pro, but I'd like to be able to limp it there instead of tow it and I'd sure like to know a real pro to take it to. Seems like the shops around here aren't capable of much more than an oil change or a brake job. I usually have real good luck in smaller towns - seems like the mechanics there usually know what they are doing. Here in suburbia ... well everyone just wants to buy new.

[APEowner]

One quick thing you could try is unplugging the tach. If the tach itself is defective it can cause all sorts of issues.

[dave5605]

Ok, wild guess time.

Be sure the outer ring on the crankshaft damper hasn't started to come loose from the inner portion. After a lot of miles the elastomeric (sp?) ring bonding the inner and outer portion of the damper starts to slip a little. I have seen timing marks off by over 2". Usually what I have seen is the outer ring also slips either forward or backwards so if you pay attention you can see it.

Otherwise you have to get #1 piston at TDC on the compression stroke and see where the timing markand rotor in the distributor are positioned.

Another problem is if you messed with the timing chain between the crank and cam it may be off 1 tooth. Been there done that too.

If you get a good timing light you can see the timing pulse/marks even when cranking the engine. Doesn't even have to be running.

[Nosman]

I'm with APEowner on this one, I've seen aftermarket tachs do some crazy stuff with ignition systems before.

[lost_cause]

i've seen a few cases where the distributor shaft was loose and it would do erratic things to the timing. cases where it was so retarded that it did not have enough power to climb a hill, and a few minutes later so far advanced it would bind when trying to start. might be worth checking the distributor to make sure.

[Fasttrack]

i've seen a few cases where the distributor shaft was loose and it would do erratic things to the timing. cases where it was so retarded that it did not have enough power to climb a hill, and a few minutes later so far advanced it would bind when trying to start. might be worth checking the distributor to make sure.


What do you mean the distributor shaft was loose? That certainly sounds like the behavior I am noticing, although I am finding that there are many causes for this behavior ;) :D

Thanks guys - I'm compiling a list of things to try (and buy :( ) when I get home tonight.

[saltmine]

Worn distributor bearings is what I believe they're talking about.

With EST, all timing functions are done electronically, and the bearings would have to be pretty bad to get the pickup coil to contact the reluctor in the housing. The high voltage contacts in the top of the cap is a different story, worn bearings would allow the rotor to strike the posts, and either break the rotor, or shatter the distributor cap. Any play in the distributor shaft is too much.

Once or twice, I've seen a distributor that's not tightened down well, and worn bearings conspire to retard the timing. But never advance it.

A buddy just got a Chevy truck, for free...Because the tach was messed up.... (Secret, keep it under your hat...)

[Flying-Phantom]

Could the lifters be out of adjustment?

[Arcane]

Could the lifters be out of adjustment?


That is a good call. It seems a lot of hydraulic lifter preload is on the high side if you go by the book numbers. I've seen it in person and some friends had the same problem.