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Please Help, Pcm/Ecm?


leanapache
11-09-2007, 09:13 PM
This thing is giving me fits. 1990 3.8 olds 88 V6, 160thousand miles, pulled into the yard, fine, next morning would not start. Turns over but has no spark. Change crank and cam sensors, now have spark at plugs but only backfires , like valve timing is wrong or plug wires were not re-attached correctly when you try to start. Has 40 lbs fuel pressure at injector rail. I was thinking it had jumped a tooth on the timing chain. Pulled timing chain cover, and valve timing marks are lined up correct. timing chain and tensioner appear fine, Compression is 120+- 10 on all six cylinders. I have visually ,verified a strong spark getting to all six sparkplugs. When you turn it over it trys to start but only gives a weak backfire out of the intake. This thing has no distributor, relying on the cam, crank, and computer ,to do all the timing advance adjustments. I put number 1 cylinder on TDC on compression stroke, using ane indicator off the top of the piston, and then put my own timing mark (because there are none) on the harmonic balancer. With a timing light it shows the spark coming almost 40 degrees tooo retarded for this thing to run. The piston is way over the top before the spark arrives. Would the E/Cdm box do this??

Mickey#1
11-09-2007, 10:37 PM
The ICM controls spark until RPM's hit 400. Are you sure the key was still in the crankshaft keyway when you reinstalled the harmonic balancer?

leanapache
11-10-2007, 06:52 PM
thanks for the reply, I pulled the harmonic balancer and keyway was fine, also looked close at the two rings or tabs that signal the crank sensor and all were ok. I tryed another coil pack and ignition modual (the electronic unit right under the coil Pack) and still the timing light shows a waaay retarded spark. I have never been able to get any error codes using the paper clip jump thing , nothing , no 12 light deal, and my diagnostic socket really only has three wires going into it . I jumped the A+B ones like my manual says, nothing blinks. What advances or chooses the spark advance amount , at cranking speed,under the 400 RPM amount you spoke of. Thanks

leanapache
11-11-2007, 11:54 AM
Boy I am the NEWBIE. I was doing something wrong on the paperclip test? Now the fan comes on as its supposed to and I get the 12 over and over. We had disconnected the battery so all other codes would be cleared? It still appears way retarded on spark and really doesnt backefire much. Will any codes be set with just cranking speed or does engine have to run? I was considering putting on a degree wheel to see if the spark was exactly 60 degrees off, (an increment 360/6) to better understand what might be the problem, or is that just wishfull thinking. It visually appears about 45 after TDC + the ten or 12 that most engines want advanced would make the 60 it now seems wrong. Any ideas. Thanks

maxwedge
11-11-2007, 01:49 PM
What kind of indicator on top of the piston are you referring to? Remember the piston dwells at tdc for about 10 degrees before it starts down. Very hard to find exact tdc this way, what referrence on the cover are you using as a pointer on the balancer? Also I do not believe timing may be your problem, try disconnecting the maf, see what happens.

Mickey#1
11-11-2007, 05:36 PM
Missing key was the only thing I could think of if the timing is really off that much. Are you sure the spark plug wires didn't get mixed up? How did you center the sensor with the harmonic balancer? I'd also like to see you check for fuel injector pulse.

http://i33.photobucket.com/albums/d61/bon2k/misc3/plugwires.jpg

leanapache
11-11-2007, 06:21 PM
I used a homemade tool that is just a sparkplug , with all the porcelian center and guts removed, replaced with a sleeve that is epoxied in that allows a 1/8 brass rod to move up and down against the piston top, as you GENTLY raise and lower the piston by hand. You do have to pay attention to that "dwell" period in the movement of the crank( looking at the amount the crank moves clock and anticlock) when the brass stays stationary, and decide where the tdc is, but it does get you close. After I marked the balancer I used a machinist type magnetic base with a pointer above the mark ,called zero. I am kind of surprised how bright (at crank speed) that my timing light is firing. Sometimes you need more rpm to get a good consistent bright light. Disconnected the maf and still a weak occasional back fire, the timing stayed about 45 after tdc , both with maf connected and then disconnected. I have sprayed ether a couple time thru-out this deal and it didn't seem to have any effect. Would the maf in some way adjust the spark advance, or do you think it's a fuel thing. Thanks

maxwedge
11-11-2007, 06:31 PM
Nice job on the timing set up, the maf can skew injector pulse and timing, but not in this case it seems. Possible the balancer has slipped on the outer hub and the cps is giving erroneous info to the pcm, the balancers are famous for coming apart on the 3.8's but usually this is accompanied by rattling noises. Mickey#1's points are also valid.

leanapache
11-11-2007, 06:55 PM
I did look at the harmonic balancer , real close , when I checked the keyway. I was suspicious where the rubber vulcanizes the thing together, maybe it had slipped. Looked good. I read #1's earlier post history, on using a 194? bulb to check the injector pulse, I will go there , but was thinking by using sprayed in either , I had eliminated the got spark? got fuel? question. Work tomorrow, but will be back on it. Thanks you two.

leanapache
11-24-2007, 03:57 PM
Still hoping for some help. The crank sensor has a locating hole that a centering spud coming out of the block,then two bolts(pretty foolproof) I did the pulse test on three of the injectors with 194 bulb, all pulsed. You can even see and smell the gas entering the cylinder with a plug out and cranking. Have triple checked the plug wires and timing order,even made sure the 3 wires under the coil pack were correct to 1-4.5-2.6-3coils .Am I correct in thinking the way 1 and 4 fires at the same time it eliminates the being 180 off ignition timing when you screw up with a regular distributor type system. When I put timing chain on.Put on a new $94 ECM no change, very little backfire when you crank and timing light has strong spark coming 40 or so degrees late. My manual talks about the electronic spark control ECS (knock sensor),allowing the ecm to keep retarding the spark to the point the motor would run sluggish. We really have worked on some motors just not with the "distributorless" feature. Any ideas, running out of X-mas money. thanks

Mickey#1
11-24-2007, 10:43 PM
I don't see how we can ignore your results with checking the timing. I'd put a cylinder on top dead center & remove the harmonic balancer. One of the gaps on the 3x interrupter ring should be lined up with the crank sensor. If it doesn't line up then I would take the balancer to a parts store & compare it to a new one. Look carefully at how the keyway lines up in relation to the gaps in the 3x ring.

Do you have the style of crank sensor that uses a pinch bolt to hold the sensor tight in the bracket? If so you should use a feeler gauge to check the gap between the sensor & the outside of 18x interrupter ring. The gap should be around .020.

leanapache
11-25-2007, 06:56 PM
I replaced the knock sensor , no change, Had both Ignition Modules checked (autozone) the original and one from a wrecking yard,we had used them both previously, but never really confirmed they were ok, just had spark with both, and problem stayed , both checked out good. Put #1 cylinder on TDC , removed harmonic balancer and marked the three gaps that very in width. Put harmonic back on, none of the 3 gaps was within the crank sensor when at the TDC. Thought "All Right " on to something.Took harmonic to zone and compared it to a new one . The 3 gaps were identical in relation to the keyway . We looked at the harmonic befor taking it back, and all agreed that it could wear right out, as far as supporting the serpintine belt, and would still hold it's 18 and 3 tab relationship with the crank sensor. It was the middle widest gap that was just about to start entering the crank sensor grooves when mark was at TDC, if that is of some help. Yes it was the pinch bolt style, and looked centered going through the slots of the crank balancer.Thanks

Mickey#1
11-27-2007, 09:29 PM
I had a chance to check the timing on my son's 99 Bonneville SSEi using a method similar to yours. We used a mirror & could shine a flashlight on the mirror & have the light reflect into the combustion chamber. I was able to watch the piston come up to TDC as my son rotated the crank with a ratchet & socket. We then put a dab of paint on the balancer & engine. It was hard to tell because the engine starts so quick but I think the timing light flashed right on TDC once or twice then moved about an inch BTDC when it started. If the balancer is 6 inches in diameter 1 inch would be about 20 degrees BTDC.

I having a hard time figuring out how your timing could be off 60 degrees. I wonder if you purchased a sensor with a faulty 3x sensor if the ICM would try to use the 18x sensor for ignition timing. When you changed the cam sensor did you check to make sure the magnet was still in the cam gear?

http://i197.photobucket.com/albums/aa182/MikeTu/IMG_8025800x533.jpg

leanapache
11-30-2007, 07:59 PM
You nailed it! Ya we did install a new magnet early on. Thanks so much for the help. Even though the crank sensor was new it must have been bad. So we made all the other changes, ignition module, ECM, knock sensor, timing chain, and nothing got better. Read your post last night and tryed another crank sensor. Fired up immediatley, timing light on about 10 advanced of our TDC mark, and ran great! Your picture quality is excellent in your posts.thanks thanks thanks

Mickey#1
12-01-2007, 09:13 AM
Great news & just in time because I was quickly running out of ideas. I've been a member of another 3.8 forum for a couple years & have read a lot of 'no-start' threads. This is the first I've seen in which someone checked timing. It's also one of the only ones I've seen that had spark, fuel at the rail and injector pulse but still refused to start. Give yourself a pat on the back for checking the timing.

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