Another no start for 92 3.1

[DOUGLASNC]

Trying to figure out if she jumped timing or maybe PCM went out. Car started dying going up hills then stalled out on level road. Found coil pack for #3 and #6 bad and replaced it. Other's arced ok so I left them alone. Didn't help starting it so I checked the fuel pressure and got 37psi with key on and engine off. Any idea's about what would cause it not to even try to hit? Considering maybe it's jumped timing or the PCM is going out. Thanks in advance for any idea's.

[Blue Bowtie]

Since the fuel pressure seems adequate, is fuel getting to the cylinders? If you manually apply fuel or a little starting fluid, does the engine fire?

If administering fuel or starting fluid produces results, are the INJ1 and INJ2 fuses intact? Is the 12VDC supply present at the injectors? What are the DC resistances of all six injectors? If one is below the 12Ω threshold it may be preventing any of them from operating (opening). With the injectors unplugged, is the ECM grounding the injectors correctly?

[DOUGLASNC]

Thanks for the quick reply. Haven't got that far yet, but will. Just found two wires (purple and yellow) leading from what looks like the coil module forward and under the front of oil pan around to other side of engine. They were twisted together and missing the insulation. Wires had been mashed together because of a bad motor mount I think. Will repair them and see what happens then. While changing fuel filter, I turned switch on and the fuel sprayed out ever where, so I'
m pretty sure the pump is ok. Just replaced the fuel pressure regulator two months ago. Also thinking about replacing the cps if fixing these wires don't help. Will get back to you with results, and thanks again for the help.

[Tech II]

I assume, this is a 3.1 "Multiport" engine? The difference between a multiport and a sequential engine is a cam sensor....multiports don't have one....so when they fire injectors, they fire them in groups of three(1-3-5, 2-4-6), instead of individually.....if one injector in that group of three is shorted, it draws too much current and the injector driver in the ECM that drives the injectors will shut down and not fire them......I think this is what Blue Bowtie is alluding to.....

If you have spark, this means the crank sensor is ok.....so get a can of carb cleaner, open the throttle body, and spray some carb cleaner into the upper plenum.....wait a few seconds, close the throttle plate....have someone attempt to start the vehicle.....spray carb cleaner at the closed throttle plate.....if car starts and runs as long as you spray, then he injectors are not firing if fuel pressure is ok.....

Many times, I have seen mice build little nests under the upper plenum and they like to eat injector harnesses.....if multiport, measuring resistance at the bulk connector, the resistance should be 4 ohms(three 12 ohm injectors in parallel)......

[DOUGLASNC]

Thanks Tech II, it's multiport, but I did change the crank sensor today. Nothing helped although it did back fire once when I first tried to start it. Then just spun over. Got to work tomorrow so may not get back to it for a few days as it will be dark when I get home, and were expecting some winter mix. Sprayed some starting fluid in it with no results also. Was by myself, so I held throttle open and sprayed. All wires and plugs are new as is fuel filter. Guess its time to remove intake and try to check those injectors out. So if I get a lower reading than 12, one or more of those three injectors are bad? Will read up some more in the Haynes manual about testing so maybe I can get a better understanding of how to do this. Tried to pull any codes by jumping terminal's A&B, but no codes came up. Just flashed 12 over and over and fan would come on. Wish it was OBDII. Thanks again guy's

[Tech II]

Looking at this diagram, you can check the resistance without removing the plenum....you disconnect the injector harness, and attach your ohm meter to the half going under the plenum.....

Let's start with the 2-4-6 injectors.......with the meter on a low ohm scale, attach one lead to the pink/blk connector in the harness and the other lead to the lt blue wire connector in the harness.......since all injectors should be about 12 ohms, 3 in parallel would read 12/3 or 4 ohms.....if one was open, it would measure 6 ohms.....if two were open, it would measure 12 ohms .....if all were open, it would measure infinite......if one injector is shorted, it will read zero......

now attach the leads to pink-blk and lt green, and as before, you should be getting 4 ohms.....some diagrams show a separate pink-blk for each trio of injectors, some only show one....

[DOUGLASNC]

Thanks again Tech II, This is great to learn. was dreading tearing it apart just to test. Wont mind so much is test calls for it though. This info isn't in the Haynes manual, and I really appreciate you're guidance here. The weather is messy now, but I'll get on it as soon as I can. Will update as soon as I can. Thanks again!

[DOUGLASNC]

Back again, I couldn't really tell what was what at the harness as their were two light blue wires and two green wires there. Took plenum off and found two injectors on cylinders one and five were pink and blue while cylinder three was green and yellow. Same thing on front side with #two and four being green and yellow, and #six was pink and blue. Probed each injector and got 2.1ohms on each. When trying to probe the harness end, it would just flash numbers all over the place.

[Tech II]

OK, here is another schematic:



the key is the light green and light blue control circuits......

What is confusing about those injectors is they are not really in the place that they actually look....if you look at the lower intake you will see a casting number(from 1-6) that the injector hole actually feeds(kind of crosses over to the opposite side)....so look at the "runners" in the lower intake going to the injector holes, and you will see the casting number of the cylinder it actually feeds...the even numbered injectors will have the light blue control wire, and the odd numbered will have the light green.....power feeds in this harness are pink for 1-3-5, and yellow(in your case) for 2-4-6......

However, the ohms reading, directly from each injector should be 12 ohms.....an ohm reading from yellow to light blue, should be 4 ohms(with injectors connected, but main harness disconnected.....4 ohms from pink to light green.....

[DOUGLASNC]

Well it's jumped timing. Swapped out the ecm with no luck. Didn't have a compression gauge, but pulled front valve cover to watch for movement of valve train. There wasn't any when cranked. Pulled all rocker arms on front bank and didn't find any bent push rods. Back bank will be a bugger to get to. Don't guess I could leave that side alone and hope for best could I? Also, will need to brush up on valve adjustment now. Thanks for all your help. Should have checked this out first.

[Blue Bowtie]

IF there is no valve motion on ANY of the valve on the left (front) bank of cylinders with the engine cranking, the chain may have failed, cam snapped, or some other mechanical failure of the valve train has occurred. It's most common for the cam to snap at the rear cylinders in this engine, leaving the front cylinders' valve train operating, but anything can happen.

As for the valve train, there will be no adjustment. Rocker pivot pedestal bolts are torqued to a value, leaving the lifters to adjust lash hydraulically. These pedestal bolts are also known to pull out of the heads, stripping the aluminum along the way. Repair of this requires installation of a thread insert, so be careful about disassembly and the torque value upon assembly.



It may be possible to remove the accessories, water pump, balancer, timing cover, and timing set with the engine in place given the extra space provided in the Lumina body, but it can still be tight.

PROCEDURE

1. Remove the air cleaner assembly.
2. Disconnect the negative battery cable. Drain the cooling system into a suitable container.
3. Remove the serpentine belt and the belt tensioner.
4. Remove the alternator-to-bracket bolts and remove the alternator, with the wires attached, then support it out of the way.
5. Unfasten the power steering pump-to-bracket bolts and support it out of the way. Do not disconnect the pressure hoses.
6. Raise and safely support the vehicle.
7. Remove the right side inner fender splash shield.
8. Remove the flywheel dust cover.
9. Using a suitable crankshaft pulley puller tool, remove the crankshaft damper.
10. Label and disconnect the starter wires, then remove the starter.
11. Drain the engine oil into a suitable container, then remove the oil pan.
12. Remove the lower front cover bolts.
13. Carefully lower the vehicle.
14. Disconnect the radiator hose from the water pump.
15. Detach the heater coolant hose from the cooling system filler pipe.
16. Remove the bypass and overflow hoses.
17. Remove the water pump pulley. Disconnect the canister purge hose.
18. Remove the spark plug wire shield from the water pump.
19. Unfasten the upper front cover-to-engine bolts, then remove the front cover.
20. Remove and discard the gasket. Clean front cover mounting surfaces.

Given all that, you may want to be certain the timing chain is the prime suspect before digging in.

[DOUGLASNC]

Thanks for your reply. That rocker arm isn't like mine. Mine aren't pedestal type. Just plain rocker arms with a half round insert and nut holding them tight. Got it tore down to where I need a puller to get harmonic balancer off. Then I can remove the timing cover. I assume this is an earlier model. Haynes didn't mention Bringing #1 piston to TDC on compression stroke, but does say on later models to set #1 on TDC (on compression stroke I assume).Does this mean that if mines the older model, I need not worry about getting #1 to TDC? Just make sure both crank shaft and camshaft marks are at 12 o'clock? Page 2D-10 in manual under removal.. Also on same page on removing the timing cover, seems like a lot stuff to remove unless I've missed something. Thanks again.

[Blue Bowtie]

If you have the early 2.8/3.1 heads they will have the straight valves and older style (hemispherical ball) rockers as you describe. That rocker assembly is from a slightly newer ('96-ish) 3.1, and I thought that came into effect in 1990/91 - Evidently I was mistaken.

You will need to get #1 to TDC to align the timing chain sprocket marks, and it may be easier to do that now unless you have a crank snout socket or other means to turn the crank with the balancer off.

[Tech II]

Wow, no valve movement on 2-4-6 push rods?

If a camshaft, there is no room for replacement......would seriously consider looking for another motor...

[DOUGLASNC]

Hadn't considered the cam braking. With timing chain off, would I be able to turn cam, or even pull it in and out some? Guess not with the lifters still in the engine. But if chain is broke or gears striped, replacing that part would let me then roll engine over and tell if valves are again working. If something catches while turning it over I'll know something's broke in there. As far as getting #1 to top dead center, I'm having a time trying to find compression stroke as the rocker arms are off on front side of engine and air escapes there as engine is hand turned. Cant reach deep enough into #1 hole to plug it with finger and feel for compression. Mark on damper is lined up with mark on timing chain cover. Is it important that I find compression stroke as the ECM will do the timing? Really appreciate all your guidance guys.