Hey guys, I could really use some help here. I've been pulling my hair out on this engine for about a month now and can't figure out what's wrong. The engine isn't in a Camaro, but this seems like the best TBI resource on the web. Thanks for any help y'all can provide!

Background on the engine: I purchased an old FJ-40 with a Chevy 350 in it. It was carbed and never ran well. Shortly after I bought it, I put on an Edelbrock aluminum intake manifold and a TBI kit from Affordable Fuel Injection. The kit has an ECM and components from a '90 pickup.

After installing TBI, I couldn't get the engine to start at all. I have a fuel pressure gauge on it and it's sitting at 12.5 psi. I pulled a plug to check spark and not only did I have spark, but the engine finally started! I put the plug back in and the engine wouldn't start again.

I have WinALDL and pulled values from the ALDL connector. The MAP sensor wasn't reading anything at all, so I thought I had my culprit. Replaced that and now it's reading values, but still no start. There are no codes when it runs, other than the EST timing code that indicates the timing is disabled.

I finally drilled out the cap over the idle screw, despite the AFI instructions saying that I'll never have to mess with that. With the idle screw turned out so that idle was at 5% throttle, the engine finally starts, but only with the computer control timing disabled (the brown wire coupler is disconnected). With it finally running, I set timing to 0 degrees. I reconnected the timing wire and it refuses to start. It'll kinda stumble a couple times, but it won't ever reach idle. This is with the idle screw still turned to 5% - it won't even stumble at the factory 0%.

Here's a couple curious items: IAC never moves from 145 value (fully extended). I went through the recalibration procedure and it appears to be working correctly, i.e. if I pull the IAC out and turn on the ignition, it'll pull the plunger in a little bit, then push it all the way out once the starter is pushed. Maybe this is expected behavior when the timing is disabled? Also, this kit did not include a knock sensor, yet WinALDL reveals a rather high knock count. I have no idea how it would be sensing knock.

I don't think it's a vacuum leak - I've tried it with the PCV pulled off the throttle body and plugged as well as the brake booster line pulled off and plugged. Also, the gaskets are new and I used Edelbrock Gasgacinch when installing.

Since the engine won't even start, I don't think the CTS or O2 are to blame. I tried it with the IAC completely removed from the engine and, other than a massive sucking sound, no change in behavior.

I have two potential ideas, but one requires a lot of work and the other requires some cash, so I wanted to run 'em by smarter folks first. 1) Cap/wires/plugs. The distributor came with the AFI kit, but did not include a cap. I'm using the HEI cap that came with the vehicle when I bought it. I don't think it'd run at all if that were the culprit, so I'm leery of buying a new one. Could it be weak, but still somewhat functional? Same for the wires/plugs. 2) Could the cam timing be off? I really don't want to pull the whole front end off the engine to check it unless that's a likely problem. The engine seems to run about the way I'd expect it to when the CC timing is disabled (except for the high throttle necessary), so I'm skeptical that it's the cam timing.

Thank you all for any suggestions you can provide! I can post up pictures or WinALDL logs if it'll help.

 

I have this mostly resolved, in case anyone else has similar symptoms and runs across this thread. It's definitely a timing issue. I did the timing calibration per normal instructions: unplug connector near distributor, set timing to 0, turn off engine, plug connector back in. This evening, I manually turned the crank until the timing lines were lined up, then popped the cap. Instead of pointing at plug 1, the rotor was well past the point. I would estimate it was about 10 degrees retarded. I shifted it to roughly 0 degrees, then fired it up. For the first time since installing the TBI, it ran with the electronically controlled timing enabled!

However, it was still running really rough. I turned the distributor by hand with the engine running until it smoothed out. Judging by how far I've turned it since it read 0 with the timing disabled, I'd say it's now about 20-30 degrees advanced from that position. It's clear off the marks by the balancer, so I can't even tell. I assuming this means something is still wrong, but at least it runs.

It has been suggested that my balancer may have rotated on the crank. Does anyone know how to check this? Do I have to remove the belt and crank pulley to find the keyway on the balancer?

TIA

 

the balancers on these cars is keyed; you can't rotate it without having some serious issues. some aftermarkets have multiple keyways though, may be worth taking a look

 

Location of the timing tab is the culprit. The moment you move away from OE configuration you have to set your own (e.i. engine specific) TDC location. When building (any) motor with after market parts you have to find #1 Cyl TDC and set balancer timing tab to match.

//RF

 

Yep, you're absolutely right. I tore down the front end of the engine and my harmonic balancer has a timing mark just before the keyway at 12 o'clock. The timing tab on my engine is integrated into the timing chain cover and is at roughly 2 o'clock. I lined up these marks when putting in the distributor, so my distributor is installed about 45 degrees off. Another question for y'all: can any 350 harmonic balancer be installed on this engine? It seems like it'll be easier to replace the harmonic balancer with one that has timing marks to match my pointer instead of replacing the timing chain cover. Thanks again!

 

Yes they are interchangeable, very early balancers had the mark right next to the keyway (2*) then it was moved to 10* & finally to 30*, the ones you look straight down at.

The 10* location is the aftermarket standard for balancers & tabs.

 

I was wrong. I was operating under the assumption that the keyway always lined up with the timing mark on the crank, regardless of the timing mark on the harmonic balancer. That must not be the case, because I just manually verified TDC via the spark plug hole and the keyway on the crank is pointing to roughly 2 o'clock. So now I'm back to square one. I have a TBI setup that runs great when the distributor is way advanced. No error codes. Here's a picture of where the distributor is turned right now. Distributor Here's a picture of me pointing to the location of the rotor under the cap when the engine is lined up at TDC. As you can see, it's way before plug 1, closer to plug 8. Rotor position If I have it advanced 30 or so degrees to get it to run right and the computer controlled timing is advancing it even more, that's gotta be, what, 50 degrees of advance to run? Something ain't right...

 

Perform a timing check with timing light.

1) You need to get a correct timing tape for your balancer (measure diameter of your balancer).

2) With Cylinder #1 piston confirmed at TDC install tape on the balancer with timing pointer set against 0 deg (on the tape). This way it does not matter which way crank key points.

3) Get engine fired, warmed up to normal operating temperature. Get a timing light going. Since you are using 90's truck stock calibration (assumed 1227747 ECM with ASDU calibration) I would expect to see 17 to 20 deg timing at idle (650RPM) on stock balancer, but in your case it may be different. Record timing value observed (on the tape).

4) Disconnect EST connector - record timing value observed (on the tape). You will probably see that timing is retarded by 17 to 20 deg from the earlier reading. Now this is where things get interesting. When you disconnect set EST connector ECM no longer controls timing. Stock truck applications call for 0 deg, but in your case - based on your observations it will be around 30 deg (on the timing tape). You need to go through these steps before you can move forward, but if you are at 30 deg you have couple of causes:
a) camshaft - crankshaft timing dots on the timing chain gear set were set in retard position (low probability, but worth a check.
b) distributor reluctor coil is plugged backwards into ICM
c) Distributor phasing is not correct.

//RF

 

Distributor was out 180 degrees. I took the timing cover off, lined up the dots and reinstalled the distributor.

My problems aren't over, though. With the distributor 180 degrees off, I was able to get it running quite well by advancing it about 30 degrees. With the distributor lined up the way it's supposed to be, I got nuthin. Not even a hint of a stumble. I've tried giving it gas, advanced it 10-20 degrees, retarding it 10-20 degrees, pulled the EST connector...none of it helped. The closest I can get is some very mild throttle body backfire. I pulled a plug to make sure I still have spark and I do. Is it possible a previous owner put in a cam designed for a different firing order? Are there any cams that fit into a Chevy 350 that don't have the normal firing order?

 

With the timing chain dots lined up, that is crank gear at 12 o'clock and the cam gear at 6 o'clock, that is TDC firing on # 6 cylinder.

With both timing chain gear dots at 12 o'oclock, which isn't what is used for cam install, that is #1 TDC firing.

The balancer ring could have slipped. This happens. It is only bonded to the damper hub via a thin rubber ring.

There are SBC cams with a 4/7 swap. Note that these are aftermarket, no stock SBC cam has a 4/7 swap.

What you need to do is to look and see where the damper timing mark is relative to the key way. Then see if it matches the timing tab.

Note that with #1 or #6 at TDC, the key way will line up parallel to the #1 cylinder. That is it will be at about 2 o'clock looking at the front of the engine.

RBob.

 

OK, missed this on the first read. With the timing mark just before the key way slot, sounds like the balancer ring slipped a degree or two. Also, this is the correct damper for use with the timing tab at about 2 o'clock.

Do this, find TDC on #1 again, be as precise as possible. The damper key way should be parallel with #1 cylinder. Then look at the timing mark and it should be lined up with the 0 mark on the tab.

RBob.

 

TDC on #1 is with the cam at 12 o'clock? Oh geez, I screwed it up. I'll return it to the way it was. Thanks! Just to clarify, the balancer ring is the outer donut of the damper, right? The solid, heavy part that surrounds the three spoke inner portion?

 

Yes to both. Cam gear dot at 12 o'clock is TDC firing on #1.

The balancer ring is the outer portion.

See the attached picture. The right hand balancer (orange) is an early style using the timing tab at 2 o'clock. Note the key way and timing mark line up.

The left hand balancer (blue) is, IIRC, from an '85 LG4 Camaro engine. This uses the timing tab that is at 12 o'clock hidden behind the water pump.

Can also see the rubber strip between the hub portion and the donut portion.

I also did some quick math and what is being referred to as the 2 o'clock position is really the hour hand at 1:30. The SBC is a 90* engine so the 45* slant of the cylinders puts it half way between 12 o'clock and 3 o'clock, which is 1:30 o'clock.

No matter, when #1 or #6 is at TDC, the key way will be parallel (1:30 o'clock) with the #1 cylinder bore.

RBob.

 

Excellent info! Thank you very much! Back to the garage...

 

I'm back. Didn't have time to work on it the last two months, but I'm giving it another go now.

As mentioned earlier, I pulled the timing cover off, lined up the engine at TDC and put the distributor in with the rotor pointing right at the #1 plug. In this position, the harmonic dampener timing slot points right at 0 on the timing chain cover marks. Perfect, right? So I button it back up, unplugged the EIC and fired it up. With the EIC disabled, it's supposed to leave the timing alone, correct? Well, it idles at 30 degrees advanced.

What would be advancing it by 30 degrees with EIC unplugged?

 

I am assuming that the EIC you are referring to is the EST/BYPASS connector?

If so, then set the timing to 0* by rotating the distributor. Note that the ECM calibration may require the base timing to be set at a different values. Such as 4* or 6* BTDC.

Setting the timing is best done with the engine warmed up.

Once set shut off the ignition, reconnect the EST/BYPASS connector and re-start the engine. The timing should now be in the 16 to 22* BTDC area. If so you are good to go.

RBob.

 

Yep, that's it. Forgive me if I'm using the wrong terminology.


It doesn't matter where the rotor was pointing with the engine turned off and at TDC? 30 degrees prior to where the #1 plug was seems like quite a bit to me. I guess I don't understand why the position of the distributor at 0* timing with the engine running and the bypass connector disconnected would be any different than the position of the distributor at TDC with the engine off. Shouldn't they be the same?

 

As the spark timing is changed the rotor to cap terminal alignment will change. This is due to the rotor being fixed to the shaft that has the trigger wheel.

The spark can be firing up to 40-some degrees prior to the cylinder reaching TDC.

Then the spark timing may be only 10* BTDC when under load at lower RPM.

With this there is only one value of SA where the rotor tip and cap terminal are in exact alignment. At all other SA values they won't be aligned, but close enough for the spark to jump.

RBob.

 

I don't think we're on the same page and I have no doubt it's because I'm not conveying the situation correctly. I've created a few cheesy MS Paint doodles that will hopefully clear up some of this.

The first picture is the orientation of the distributor with the engine turned off and the timing chain cover removed to verify that the engine was at TDC of the proper stroke (both cam and crank wheels at 12 o'clock). The distributor was inserted such that the rotor pointed directly at the plug wire going to cylinder #1. In the doodle, I have a little "1" in the approximate location of this plug and I also have the square on the side indicating where the tach and coil+ wires attach.
In this position, if I turn on the engine with the ESC disabled, the timing is at 30 degrees advanced. This is what I think is the root of the problem. As far as I understand engines, it should be at 0 degrees advanced at this point. I did not check timing in this position with ESC plugged back in, but I would estimate it's somewhere around 0 BTDC and 10 degrees ATDC.



The next picture is the orientation of the distributor after setting it to 0 degrees with the ESC disabled. As you can see, I turned it clockwise looking down from above about 30 degrees. In this position, I can plug the ESC back in and it'll just barely run. Timing light indicates it's WAY retarded. Probably 20-30 degrees ATDC.



The final picture shows the distributor orientation when I turn it counterclockwise until it runs well. It's approximately 30 degrees counterclockwise from the position in the first picture. In this position, it will not run at all with ESC disabled, presumably because it's trying to run at 30*initial advance + 30* additional advance from turning counterclockwise = 60* total advance. In the position and with ESC enabled, timing light indicates overall timing of about 12 degrees BTDC. I haven't tried advancing it more than that.



As I tried to explain earlier, I think something has to be wrong with the rotor position. I don't believe it should immediately hop to 30 degrees advanced with the ESC disabled, although no one has said that's abnormal behavior. Is there anything else that would change the timing that much? The odd part is that when it's in the position shown in the final picture, it runs real well.

Any and all suggestions welcome. Thanks!

 

1st - great diagrams!

I am not sure at this point, but I would simply try to locate (beg or borrow) another distributor. I have never seen anything like this before. Usually, distributor shaft needs to be turned to next tooth to get the body aligned and that's about it.

As I have mentioned in the earlier post - reluctor coil phasing could be causing this weird behavior. Another possibility is a weak magnet in the cage (speculation). I have rebuilt about a dozen distributors with new reluctor coils. For the most part it is a simple drop in installation - nothing like what you are describing.

//RF

 

The polarity of the pickup coil in the distributor is reversed.

Either replace the pick up coil or switch the two wires in the connector.

RBob.

 

I didn't see this sooner but it is a common problem on conversions.
As Bob said, the P and N terminals on the ignition module are reversed.
This will give about a 20* error in timing.

The easy check is to mechanically set TDC and then crank the engine and check with a light.
If it's off by 20* then swap the leads and recheck.

 

Thanks for all the help, guys! I looked into the pickup coil once before, but it looked like the wires were in a plastic coupler and couldn't have been switched the wrong way, so I didn't mess with them. They must be crossed at the other end or something. I'll swap those tonight. If that doesn't do it, I'll swap the distributor.

Thanks again!

 

I flipped the P and N terminals and now it's 30 degrees retarded when the engine is at 0* (instead of 30 degrees advanced previously). Guess it's time to find a different distributor.

 

I hate to say it but this is the same as your second picture. When the timing mark on the damper moves toward the passenger side of the vehicle, that is more advanced.

The other thing is: what is the BCC of the PROM that is in the ECM. If it is for an engine with a different cylinder count the spark timing will be way off.

The BCC is the 4 letter code on the silver label.

RBob.

 

Sorry, forgot to mention that the 30 degrees retarded I was seeing yesterday was with ESC disabled, so it wasn't quite like the second picture. And yea, the mark on the damper was at about 3 o'clock, way past the timing marks in a clockwise direction.
That said, I felt like I didn't give it a fair shake in that configuration, so I just gave it another shot. P and N terminals reversed, disabled the ESC and turned distributor until timing light said 0*. Plugged ESC back in and it actually runs pretty well. Timing light indicates advance of about 36 degrees. Does that sound about right for a cold engine? I still have the waterpump and front end accessories off the engine so I have a better view of the damper, which means I can't run it long enough to get it warm, yet. If it sounds like I'm on the right track, I'll button it all back up and let it get warm.
I forgot to get the BCC. I'll get that next time I'm out there.

 

36 degrees with engine very cold is probably a touch too high (I would expect to see about 30 deg once it fires), but SA should drop very quickly to about 20 degrees as engine warms up at idle (stock idle RPM around 600 RPM). At idle most stock BCC bounce SA between 16 and 20 deg. I use dial back timing light - it is a lot easier to see the bounce around main (TDC 0 deg) notch!

Try to get BCC code. Looks like P/N pin swap on reluctor coil terminal may have done the trick.

//RF

 

I thought I read in one of your post that you had a yellow connector on the pick up.
To me that means it was from an olds distr that rotates opposite of the chevy.
The standard connector is white and has the green and white wires.

The connector color and the 20* change in timing are good indicators for reversed leads.

 

Just wanted to post up a final resolution to this for posterity. You guys were on the right track - it was the pickup coil. I'm not sure if it was the right one or not, but it definitely wasn't healthy. The kit from AFI included the entire lower half of the distributor, so I had never had it apart that far. After replacing the prom and the ignition module did nothing, I decided the pickup coil would be the absolute last item I'd replace. If this didn't do it, I was gonna switch back to the carb.

When I removed the coil to put in the new one, this is what I found. Eureka! It's difficult to tell in the photo, but the two contacts from the wires aren't even touching anything.



Such a shame that I couldn't see the damage to the coil earlier. It was extremely easy to set the timing with the new coil and now it purrs like a kitten. Thanks to all for your incredible assistance!

 

And thanks for letting us know what the actual problem was.

It´s very easy to forget sending that last post telling everyone else the solution.