need mechanical help - non VW
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- IAC Addict!
- Location: Metro Detroit
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need mechanical help - non VW
Late last summer bought a 95 pontiac bonneville for my step daughter as her first car. Has the venerable 3.8 V6 with about 110k miles. Has a hard start problem that I am at my wits end trying to solve. After it is thoroughly warmed up ... say 30 min of driving around... it will start fine the first 15-20 minutes after you turn it off. But between 20min and 45-50 min if you try to start it, it cranks like crazy but won't fire. but after it sits for 30 min or so, starts fine. It is EXTREMELY consistent about the timing and not starting. If it was carburated I would think vapor lock, but that obviously isn't the case. It's been plaguing me for 3 - 4 months now. I've posted on a board specific to this model, and pretty much have tried / replaced everything recommended...no dice.
This what has been done:
- swapped coil packs
- swapped ignition control module
- new idle air control valve
- cleaned throttle position sensor and MAF sensor
- replaced upper and lower intake manifold gaskets as well as new upper manifold and PCV valve
- new crank position sensor
- new T-stat
- new coolant temp sensor
- new fuel pressure regulator
- new fuel filter
- blew out air filter (looked pretty new)
- flush n fill radiator
- new plugs
Some more stats:
- fuel pressure while running is a rock solid 34 psi - no wavering. creeps up to 40 if it sits, so don't think it is a bleed down issue.
- vac is 18" ....little low, but again rock solid
- When you get close to the witching time of 15 minutes it will be hard to start and will 'chug' with an oscillating idle for about 30-60 seconds and then it 'clears its throat'. almost like it is running rich??
- oil pressure is a low (about 15 psi at idle) unless i run a qt of lucas oil in it - that brings right back up to spec.
Obviously it is heat / heat sink related. I'm at a loss... engine needs spark, gas, and compression in the right sequence to start
This what has been done:
- swapped coil packs
- swapped ignition control module
- new idle air control valve
- cleaned throttle position sensor and MAF sensor
- replaced upper and lower intake manifold gaskets as well as new upper manifold and PCV valve
- new crank position sensor
- new T-stat
- new coolant temp sensor
- new fuel pressure regulator
- new fuel filter
- blew out air filter (looked pretty new)
- flush n fill radiator
- new plugs
Some more stats:
- fuel pressure while running is a rock solid 34 psi - no wavering. creeps up to 40 if it sits, so don't think it is a bleed down issue.
- vac is 18" ....little low, but again rock solid
- When you get close to the witching time of 15 minutes it will be hard to start and will 'chug' with an oscillating idle for about 30-60 seconds and then it 'clears its throat'. almost like it is running rich??
- oil pressure is a low (about 15 psi at idle) unless i run a qt of lucas oil in it - that brings right back up to spec.
Obviously it is heat / heat sink related. I'm at a loss... engine needs spark, gas, and compression in the right sequence to start
1976 VW Bus aka tripod
FI ...not leaky, and not so noisy...and she runs awesome!
FI ...not leaky, and not so noisy...and she runs awesome!
hambone wrote: There are those out there with no other aim but to bunch panties. It's like arguing with a pretzel.
- Randy in Maine
- IAC Addict!
- Location: Old Orchard Beach, Maine
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Re: need mechanical help - non VW
Does the check engine light come on?
How about the crank positioning sensor? (of course I don't even know if it has one).
How about the crank positioning sensor? (of course I don't even know if it has one).
79 VW Bus
- RSorak 71Westy
- IAC Addict!
- Location: Memphis, TN
- Contact:
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Re: need mechanical help - non VW
When it's not starting is the time to diagnose this. It's easy to provide some fuel, just pull off a vacuum hose on the intake and spray some engine starting fluid in the hole. It it still doesnt start you know you have a spark problem. it it does start fuel.
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.
- SlowLane
- IAC Addict!
- Location: Livermore, CA
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Re: need mechanical help - non VW
Grasping at straws here: intake air temperature sensor?
'81 Canadian Westfalia (2.0L, manual), now Californiated
"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett
"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett
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- IAC Addict!
- Location: Metro Detroit
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Re: need mechanical help - non VW
- replaced the crank position sensor (yup, has one). And no check engine light.
- replaced the idle air control valve ... if that's what is meant by the air temp sensor... didn't replace the MAF.
- good call on squirting starting fluid down a vac line ... however, that will only work if it is running lean...not rich :) It's acting like it is running rich...if i'm just over the witching time and it acts like it wants to start, if i give it partial throttle, or even WOT, all positions seem to make it worse.
I threw in the towel and dropped it at my trusted local indy tonight.
- replaced the idle air control valve ... if that's what is meant by the air temp sensor... didn't replace the MAF.
- good call on squirting starting fluid down a vac line ... however, that will only work if it is running lean...not rich :) It's acting like it is running rich...if i'm just over the witching time and it acts like it wants to start, if i give it partial throttle, or even WOT, all positions seem to make it worse.
I threw in the towel and dropped it at my trusted local indy tonight.
1976 VW Bus aka tripod
FI ...not leaky, and not so noisy...and she runs awesome!
FI ...not leaky, and not so noisy...and she runs awesome!
hambone wrote: There are those out there with no other aim but to bunch panties. It's like arguing with a pretzel.
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- IAC Addict!
- Location: Metro Detroit
- Status: Offline
Re: need mechanical help - non VW
Took it to a local indy mechanic. Said it was an O2 sensor and the fuel pump (pressure was reading low...which I knew; about 34 psi) to the tune of $860. O2 sensor made sense.. I could see heat sink issues effecting this. Fuel pump didn't; why would it pump fine 15 min after shut - off, then not pump fine for the next 30 min, then pump fine after that!?
I asked if he could be certain this would fix the problem, and he said no. I only had him replace the O2 sensor.... we will see.
I asked if he could be certain this would fix the problem, and he said no. I only had him replace the O2 sensor.... we will see.
1976 VW Bus aka tripod
FI ...not leaky, and not so noisy...and she runs awesome!
FI ...not leaky, and not so noisy...and she runs awesome!
hambone wrote: There are those out there with no other aim but to bunch panties. It's like arguing with a pretzel.
- RSorak 71Westy
- IAC Addict!
- Location: Memphis, TN
- Contact:
- Status: Offline
Re: need mechanical help - non VW
He wanted nearly $900 to do those 2 jobs? Thats completely outrageous. The fuel pump is about 3 hours and the egr maybe 1.
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.
- Amskeptic
- IAC "Help Desk"
- Status: Offline
Re: need mechanical help - non VW
TrollFromDownBelow wrote:Took it to a local indy mechanic. Said it was an O2 sensor and the fuel pump (pressure was reading low...which I knew; about 34 psi) to the tune of $860. O2 sensor made sense.. I could see heat sink issues effecting this. Fuel pump didn't; why would it pump fine 15 min after shut - off, then not pump fine for the next 30 min, then pump fine after that!?
I asked if he could be certain this would fix the problem, and he said no. I only had him replace the O2 sensor.... we will see.
Heat sink issues come in two flavors:
LEAN
leaking check valves cause boiling in the lines - starvation after about five to 30 minutes of sitting
fuel pump has one, pressure regulator has the other
RICH
a leaking cold start injector will flood the intake with a pool of gasoline and individual injector leak is much less likely to cause a global starting issue
02 sensor has nothing to do with a transient starting problem. If it is bad, it affects engine operation across the operating range.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles
-
- IAC Addict!
- Location: Metro Detroit
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Re: need mechanical help - non VW
Not sure if it has a cold start injector....nothing I've read has made mention of it. It does have an idle air control valve, which I've replaced. I'm leaning towards LEAN, specifically the fuel pump based upon low PSI readings ...runs at 34 supposed to be at 40. Fuel pump is the likely culprit. Also, I replaced the fuel pressure regulator already.Amskeptic wrote:TrollFromDownBelow wrote:Took it to a local indy mechanic. Said it was an O2 sensor and the fuel pump (pressure was reading low...which I knew; about 34 psi) to the tune of $860. O2 sensor made sense.. I could see heat sink issues effecting this. Fuel pump didn't; why would it pump fine 15 min after shut - off, then not pump fine for the next 30 min, then pump fine after that!?
I asked if he could be certain this would fix the problem, and he said no. I only had him replace the O2 sensor.... we will see.
Heat sink issues come in two flavors:
LEAN
leaking check valves cause boiling in the lines - starvation after about five to 30 minutes of sitting
fuel pump has one, pressure regulator has the other
RICH
a leaking cold start injector will flood the intake with a pool of gasoline and individual injector leak is much less likely to cause a global starting issue
02 sensor has nothing to do with a transient starting problem. If it is bad, it affects engine operation across the operating range.
Colin
It does idle smoother with the new O2 sensor. Just started it up after letting it sit for 20 minutes. It DID start, although had a slight bobble after it fired. Although it normally would not start, or start but run really rough for 20 seconds so this would be a big improvement, however, I'm not convinced it is fixed. It may be a combo of O2 + weak FP. But even if the O2 bought me a month or so, that's good.
1976 VW Bus aka tripod
FI ...not leaky, and not so noisy...and she runs awesome!
FI ...not leaky, and not so noisy...and she runs awesome!
hambone wrote: There are those out there with no other aim but to bunch panties. It's like arguing with a pretzel.
- DjEep
- IAC Addict!
- Location: Nowhere, Fast
- Status: Offline
Re: need mechanical help - non VW
If it happens again, check the fuel pressure when it's not starting. I'd even check the fuel pump electrical. I know Hondas from the early 90's would do that same thing due to cracking solder in the main fuel relay.
Also, sniff the tail pipe when it's doing so. If it's flooding, you'll smell it.
Also, sniff the tail pipe when it's doing so. If it's flooding, you'll smell it.
"Live life, love life. Enjoy the pleasures and the sorrows. For it is the bleak valleys, the dark corners that make the peaks all the more magnificent. And once you realize that, you begin to see the beauty hidden within those valleys, and learn to love the climb." - Anonymous
Do you want to Survive? Or do you want to LIVE?
Do you want to Survive? Or do you want to LIVE?
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- IAC Addict!
- Location: Metro Detroit
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Re: need mechanical help - non VW
Based on what I've read (here included), and what have been told by other ASE mechanics... as well as process of elimination I believe it is a bad fuel pump. It IS low on pressure (checked this myself). I'm going to do the job myself though ... only $100 for a brand new oem A/C delco fuel pump vs $550-$650 for someone else to do it. That's next weekend's project.
1976 VW Bus aka tripod
FI ...not leaky, and not so noisy...and she runs awesome!
FI ...not leaky, and not so noisy...and she runs awesome!
hambone wrote: There are those out there with no other aim but to bunch panties. It's like arguing with a pretzel.
- Amskeptic
- IAC "Help Desk"
- Status: Offline
Re: need mechanical help - non VW
You'll have fun.TrollFromDownBelow wrote:Based on what I've read (here included), and what have been told by other ASE mechanics... as well as process of elimination I believe it is a bad fuel pump. It IS low on pressure (checked this myself). I'm going to do the job myself though ... only $100 for a brand new oem A/C delco fuel pump vs $550-$650 for someone else to do it. That's next weekend's project.
I did a BMW 540 fuel pump at a Chevron station at Tapahatchipeiwhatchamacallit Summit in 2007, with a totally full tank of gas just having been put in to stave off my own worsening fuel starvation issues.
When you think of what that depth of petroleum liquid can do to propel a 3,700 lb car 250 miles!!, you put out your cigarette as you lift the pump out of the tank.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles
- SlowLane
- IAC Addict!
- Location: Livermore, CA
- Status: Offline
Re: need mechanical help - non VW
And you use non-ferrous tools to loosen and tighten the pump lock-ring, because you don't want any chance of sparking at all, no no no.Amskeptic wrote: When you think of what that depth of petroleum liquid can do to propel a 3,700 lb car 250 miles!!, you put out your cigarette as you lift the pump out of the tank.
Wait, a whole 250 miles on one tank? Boy, that is a tank!
'81 Canadian Westfalia (2.0L, manual), now Californiated
"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett
"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett