'90 Bonneville has spark, and normal fuel pressure via fuel pressure tester. Engine was running fine on Saturday night, and when attempted start Sunday morning it would not start. Occasionally, it sounds like it wants to start, but kinda coughs and backfires thru intake but won't turn over. What should we look at now?

Sounds a lot like a crank or cam sensor to me. They don't always throw a code like they should.

_________________

WHITE WHINE - 1992 SSE Supercharged 236.26 ci (.040 Over) 15.090 at 90.2 MPH on old engine w/ slipping trans & melted O2 sensor - Gen 3 M62 and matching TB, Gen 2 Pully, Zillamotorsports Ported LIM, YT 1.72 Roller Rockers, SII FPR & Injectors, Hypertech Thermomaster chip w/ 160 Thermo, TransGo Shift Kit, Infinity/Pioneer Speakers & a 10" Alpine Type R Sub, all the watts, 140 amp Alternator, Ricepipe CAI w/ heatshield, Pilot Angel Eye Foglights, Clear Corners, '02 17" Chrome Bent 5's, Magnaflow F-Body Muffler and Hi-flo Cat, Ceramic Coated Ported Exhaust Manifolds, Fan Override, Monroe Reflex struts, red calipers
2009 G8 GT - Sport Red Metallic, loaded, SOLO Axlebacks, Rotofab Intake, Tuned, autodim mirror, removed intake manifold cover, HSV GTS triple gauge pod, two tone red-hot shifter and HSV SuperSport steering wheel, GXP rear sway bar and diffuser, 3.45 diff and various Camaro suspension bits, LED Taillights

Is it possible to tell if a crank sensor is bad without pulling the balancer and just replacing it? The plugs were firing, wouldn't it not fire if crank was bad?

I'd think it was more likely the cam sensor then. There's a way to probe it, I don't know what it is off hand though.

_________________

WHITE WHINE - 1992 SSE Supercharged 236.26 ci (.040 Over) 15.090 at 90.2 MPH on old engine w/ slipping trans & melted O2 sensor - Gen 3 M62 and matching TB, Gen 2 Pully, Zillamotorsports Ported LIM, YT 1.72 Roller Rockers, SII FPR & Injectors, Hypertech Thermomaster chip w/ 160 Thermo, TransGo Shift Kit, Infinity/Pioneer Speakers & a 10" Alpine Type R Sub, all the watts, 140 amp Alternator, Ricepipe CAI w/ heatshield, Pilot Angel Eye Foglights, Clear Corners, '02 17" Chrome Bent 5's, Magnaflow F-Body Muffler and Hi-flo Cat, Ceramic Coated Ported Exhaust Manifolds, Fan Override, Monroe Reflex struts, red calipers
2009 G8 GT - Sport Red Metallic, loaded, SOLO Axlebacks, Rotofab Intake, Tuned, autodim mirror, removed intake manifold cover, HSV GTS triple gauge pod, two tone red-hot shifter and HSV SuperSport steering wheel, GXP rear sway bar and diffuser, 3.45 diff and various Camaro suspension bits, LED Taillights

Magnet for the cam sensor could have fallen off?

It happened on my 88 Buick, it would t want to start or if it did it would die.

Just pull the cam sensor and then turn the motor over by hand. You should see a little black thing (plastic, with magnet inside) if this is missing that's your problem.

The sensor itself could be bad as well.

If that magnet is missing I found a very good way to replace it without ripping the motor apart

_________________
Clay
1997.2 40th SLE-138k
1968 Bonneville 400ci w/TH-400-40k
1999 GMC Suburban SLT-191k
2005 Escalade 253k-GINA

I'm not sure of your assertion that the Interrupter Magnet has fallen off. My mother in law has an 88 Bonneville that runs fine with the 41 code and I have a '91 Oldsmobile and years ago the Interrupter fell off giving me a Code 41 that would not go out, but the engine still ran just fine. In this situation I have NO CEL at all, and the engine will not start. When I get a chance I'll try to see if I can see if the magnet has come off.

A failed mass airflow sensor could do this as well, to test just unplug it. Or low fuel pressure.

_________________
Boost addict


The Fleet:
'93 SSEi - Twincharged + manual Build thread
'97 Camaro - Top swap
'05 STS - V8, AWD, her DD
'92 Trofeo - Fair weather DD
'99 Montana - top swap 3800
'04 Sierra 2500HD - LLY Duramax

Current project:
Something cool, trust me.

Upcoming projects:
'92 Bonneville SSE
'87 LeSabre T-type
'67 LeSabre

Gone to greener pastures:
'84 Sierra Classic - Twin turbo 3800
'97 LeSabre - Top swap

RIP:
'86 LeSabre - pictures
'93 SE - L67

I thought of the MAF....is there a way to test it? I tested the fuel pressure with my gauges and it was in the normal range.

Just unplug the MAF. That'll give it some baseline flow numbers to idle off of. It'll help you rule it out almost right away.

Just to be sure, are the injectors actually pulsing? Do you smell unburnt fuel from the exhaust when attempting a start?

_________________
John
Now: '15 Toyota Prius III | 134 hp 2ZR-FXE | Silver | 36k
Now: '03 Honda CR-V AWD | Slow 4-Cylinder | Dirt | 180k
Then: '07 Ford Fusion SEL | 221hp Gen I VVT Duratec 3.0 V6 | Tungsten Silver | 150k
Then: '99 Toyota Avalon XL | 200hp 1MZ-FE 3.0 V6 | Diamond White | 189k | Sold: July 2015
Then: '11 Ford Fusion SEL | 240hp Gen II VVT Duratec 3.0 V6 | Ingot Silver | 84k | Totaled: Oct 23 '14 (Rear-Ended)
Then: '96 Buick Park Avenue Ultra | 240hp Series II L67 | Medium Dark Lichen | Bought: JAN 11 @ 135k | Accident: FEB 3 '12 | Crushed: MAR 1 '13 @ 153K
Then: '98 Pontiac Bonneville SSE | 205hp Series II 3800 L36 | Topaz Firemist | Bought: NOV '09 @ 74k | Accident: MAY 28 '10 | Crushed: MAR 15 '11 @ 84k
Then: '93 Pontiac Bonneville SE | 170hp Series I 3800 L27 | Dark Yellow Green | Bought: JULY '07 @ 92k | Sold: JULY '12 @ 118k
Then: '89 Pontiac Bonneville LE | 165hp 3800 LN3 | Medium Garnet Red | Bought: JAN '05 @ 117k | Sold: SEP 30 '07 @ 152k

I'll have to check....weather got nasty while working and had to quit....seems to me that I did smell a bit of fuel. Car was running great on Saturday, would not start on Sunday. I did notice what seemed to be coolant around the base of the intake on the right side. This leads me to wonder if the Intake gasket is shot (like in so many 3800's) causing coolant to flow into cylinder. We'll check these things toward the end of the week.

Easy way to tell if it is fuel or ignition related for a no start issue...

Key in the "Off" position, open the throttle wide open and spray a good shot of starting fluid into the intake. Let off the throttle then try to start it. If it fires right up for a second then your issue for no start is a fuel issue, if nothing changes then you have an electrical / ignition problem.

_________________
Ryan

2003 Bonneville SSEi - The Black Mirror SOLD!
2002 Bonneville SE - The Mutt Complete 2004 SLE interior, drivetrain, and body harness swap, ECC swap, HUD swap, black GXP wheels, GXP headlights and tinted tails - SOLD
2003 BMW 540i M Sport, 2001 BMW X5 4.4i, 2010 GMC Acadia, 2017 Grand Design Imagine 3150BH
1982 Cutlass Supreme - The fun one

Got a MAF for you here:
for-sale-or-trade/topic30803.html

_________________
90 SSE Bonneville Sold but not forgotten.

Will a leaking upper intake gasket (it has the aluminum intake, not the 2 piece) keep a car from starting? I've had a leaky one before, and the car ran fine.

Yeah, but only if you've hydrolocked the engine. Otherwise, I've personally never heard of an LN3 having a LIM gasket that was bad enough to cause an issue like that.

Have you done any of the other tests to rule out MAF & Fuel issues?

_________________
John
Now: '15 Toyota Prius III | 134 hp 2ZR-FXE | Silver | 36k
Now: '03 Honda CR-V AWD | Slow 4-Cylinder | Dirt | 180k
Then: '07 Ford Fusion SEL | 221hp Gen I VVT Duratec 3.0 V6 | Tungsten Silver | 150k
Then: '99 Toyota Avalon XL | 200hp 1MZ-FE 3.0 V6 | Diamond White | 189k | Sold: July 2015
Then: '11 Ford Fusion SEL | 240hp Gen II VVT Duratec 3.0 V6 | Ingot Silver | 84k | Totaled: Oct 23 '14 (Rear-Ended)
Then: '96 Buick Park Avenue Ultra | 240hp Series II L67 | Medium Dark Lichen | Bought: JAN 11 @ 135k | Accident: FEB 3 '12 | Crushed: MAR 1 '13 @ 153K
Then: '98 Pontiac Bonneville SSE | 205hp Series II 3800 L36 | Topaz Firemist | Bought: NOV '09 @ 74k | Accident: MAY 28 '10 | Crushed: MAR 15 '11 @ 84k
Then: '93 Pontiac Bonneville SE | 170hp Series I 3800 L27 | Dark Yellow Green | Bought: JULY '07 @ 92k | Sold: JULY '12 @ 118k
Then: '89 Pontiac Bonneville LE | 165hp 3800 LN3 | Medium Garnet Red | Bought: JAN '05 @ 117k | Sold: SEP 30 '07 @ 152k

I put my fuel pressure gauage on it, it was to specs.; and I put my spark tester on it and it had good spark. Car tries to start, even sounds like it's about to, and then just kinda "coughs" and backfires thru the air plenum and won't start.

Try starting it with the accelerator all the way down. This cuts off the injectors and helps to clear the cylinders if it is flooded. You can also pull all the plugs and see if they are fouled or wet. Also try to turn it over with the plugs out.

How were the codes pulled? was it with a tool or the paper clip method?

Being that you have no codes, blank the ECM( remove the negative battery cable for 1 minute ) see if tries to start or does the exact same thing...

When it tries to start is it backfiring through the intake...

I have an AutoXray..... after much work, would you believe we found the problem.... it was a very cruddy fuel filter. I was thrown off due to the fact that I had "normal" fuel pressure at the fuel rail with my fuel pressure gauge. Guess you learn something every day. Running great! Glad it was a simple inexepensive fix, but just blown away that the fuel filter was so nasty and I had such a strong fuel flow at the rail.

Hrmmm... odd. I was thinking you would spot something like that because it is not holding the fuel pressure while cranking...

...and here I was thinking there may be an issue with the ICM PCM handoff.

_________________
~Randall~


1993 Buick Park Avenue - 197k - Some odds and ends done - Simply won't die
1994 Buick Regal - 78k - Bone stock - Always ready for a good kicking
1990 Oldsmobile 88 - Gone to a better place

Also, sounds like it's time to find a new gas station

_________________
Boost addict


The Fleet:
'93 SSEi - Twincharged + manual Build thread
'97 Camaro - Top swap
'05 STS - V8, AWD, her DD
'92 Trofeo - Fair weather DD
'99 Montana - top swap 3800
'04 Sierra 2500HD - LLY Duramax

Current project:
Something cool, trust me.

Upcoming projects:
'92 Bonneville SSE
'87 LeSabre T-type
'67 LeSabre

Gone to greener pastures:
'84 Sierra Classic - Twin turbo 3800
'97 LeSabre - Top swap

RIP:
'86 LeSabre - pictures
'93 SE - L67