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Mom’s 90 Regal with 40k miles crank no start

49roper

New member
7
0
1
Buick Ownership
1990 Regal
Car just quit. It will fire on 2 cylinders when cranking but no start. No codes. New crank sensor. New ignition module. Good compression.
Great fuel pressure, holds. Good spark to new plugs. Spray intake, no change ( must be ignition...) Good power to injectors. Suction on intake when cranking. Coils all have good spark to plugs. No backfire or timing chain symptoms. New ECM, reflashed. Converter clear. Gas good. Grounds all refreshed. Feels like to me like the crank sensor is only picking up signal for 2 cylinders on each rotation for one coil. Oil residue buildup on crank killing signal for other 2 coils? Car has been a town car all it’s life, 2 oil changes a year. Probably Pennzoil which may explain gunk buildup. Just say’n. All the above work and the car is exactly as it was when I got it. I’m open for suggestions!
Thanks for your consideration.
 

CorvairGeek

3.8L Member
285
72
28
The Gem State
Buick Ownership
1996, 92 Buick Century
Is this a 3800 or a 3.1 V6?
Check for shorted injectors, i.e. less than 12 ohms. First generation Multitec injectors can short enough to kill the engine, due to driver circuit design.
 

49roper

New member
7
0
1
Buick Ownership
1990 Regal
3.1, can’t believe I didn’t include that. If they are shorted, will new injectors fix it or will I have to get into the driver circuit.
Thanks, makes sense.
 

CorvairGeek

3.8L Member
285
72
28
The Gem State
Buick Ownership
1996, 92 Buick Century
Replacement of the injector(s) is the fix. Unplugging a shorted injector will allow the engine to start and run with the cylinder not firing.
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49roper

New member
7
0
1
Buick Ownership
1990 Regal
I didn’t think my last reply through, must of been too early for clear thinking. As long as I’m in there, may as well do them all and be done.
I’ll let you know how it goes, thanks again.
 

49roper

New member
7
0
1
Buick Ownership
1990 Regal
Been awhile since I could work on the car but I get the same results when I feed even starting fluid into the intake which tells me it has to be an ignition problem. New module and ecm, plugs and coils have good spark and no bent pins in the connectors. New plugs are fouled.
Thanks for the input.
 

49roper

New member
7
0
1
Buick Ownership
1990 Regal
Tested injectors and replaced 2 that were under 12 ohms. Absolutely zero change. I’m starting to think cam chain or tensioner failure, although very rare on this motor, I need to know if the cam is still in the correct spot. A little tougher w/o a distributor... Also, engine number on VIN says it’s a Chevy 3.1 not a Buick.
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Regal LTD Coupe

Active member
166
31
28
Buick Ownership
1993 Buick Regal Limited coupe 3800 (1991 Cadillac Fleetwood coupe 4.9 & 1990 Lincoln LSC SE 5.0 HO)
Could be the 3.1 comes from a line of Chevy motors (I don't know it that well) while the 3.8 came from a line of Buick motors. They were all used in different GM cars; my Pontiac had a "Buick" 3800.

No one's suggested it yet but don't overlook the catalytic converter and its innards clogging the muffler (has happened to me on a '91 Cadillac). It's old enough, though the mileage is so low it might be a surprise. Then again the 3.1 was never considered as great a motor as the 3.8 so who knows if it dumps a bit of fuel into the cat or what? You said 2 of the injectors were bad so I suppose it's a possibility. If it were my car I guess I would cut the line before the cat and try to start it and if I decided it's not that would either weld it up or use a to put it back together with an exhaust clamp. Sucks but I don't know how else I'd check this, other than having someone else crank the ignition while you have your hand at the exhaust. When my Cadillac cranked and didn't want to start (and when it did it was noisy and by the end couldn't make it up a slight hill) I had already bought a Magnaflow cat and muffler years before and said what the hell and had them welded in and sure enough the car started right up and blew the remains of the cat out the muffler (which thankfully being a Magnaflow goes straight through with no restriction).
 

49roper

New member
7
0
1
Buick Ownership
1990 Regal
Thanks for the input. I already cut a slot out of the pipe before the converter with no change to condition.
Bout ready to send it to salvage, need the room in the shop when real winter hits.
Thanks again.
 

HotZ28

Full Member
7,207
390
83
Buick Ownership
1996 Roadmaster Limited Collectors Edition 58k - 1996 PAU
If you have good spark to all the plugs, adequate fuel pressure, all injectors firing, the engine it should start with adequate air. That is all it takes for an engine to start! I have never seen an 3.1 engine with 40k miles have a timing chain issue! Som Thing Wong here in the diagnosis. Could it possibly be a security issue, or oil soaked/cracked wires from the crank sensor to the ICM? Have you installed noid lights on all the injectors to confirm they are firing?
 

49roper

New member
7
0
1
Buick Ownership
1990 Regal
If the injectors weren’t firing, it would start with starting fluid into the intake. No? Maybe I’m missing something because there is no change at all with starting fluid. Rewired the crank sensor to the module and I don’t believe there is any security on the car. Not that I can find anyway.
Thanks for the input!
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