I have 1997 2500 3.9L Sometimes it's hard to start sometimes it starts right up. I've replaced plugs and wires, MAP, IAC, and ambient air temp sensor nothing seems to work. This morning drove to work, about 8 miles no problems 50 degrees outside. When I was coming home it wouldn't start, and then stalled at every light. 80 degrees outside. When it's in neutral it still stalls and sometimes it starts right up and then stalls. Any help would be awesome. I'm about to yank my hair out.
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Gas pump read 50 psi constant. Took it for a spin drove 17 miles no problem. Came home let it sit for 2 hours drove it to the corner and it stalled at stop sign. Went to store and pushed brakes heard hissing noise and car stalled managed to hear hissing 2 other times each time car stalled. Now can't recreate the hissing noise and car hasn't stalled.
The Hissing noise is indicative of a vacuum leak to the power brake booster. The vaccuum hoses to it, the check valve or the booster itself.
15 seconds after the engine is shut off, the brake pedal should still feel normal for one maybe 2 pumps. If it is rock hard, the booster has a leak.
Massive vacuum leaks will cause stalling, rich running and loping, but not so much hard starting.
Temperature differences might be causing the intermittent factor of your symptoms as the vacuum hoses expand and contract, become more flexible and less so.
Could the heat be effecting the crankshaft sensor? The power booster is definitely causing the stalling. Just trying to figure out why it won't start in the parking lot but will start under my car port.
I have also seen a weak battery or poor battery terminal connections cause your same conditions on a '98 b2500. Do you have a Digital Multi Meter? Harbor Freight sells a surprisingly accurate model for 8$ sometimes on sale for 3$.
Your battery should read 12.6 volts minimum 1 hour after shutting off the engine. If it is not, put it on an automatic wall charger overnight(minimum 10 amps) then test the voltage. The surface charge should dissipate in about 4 hours, and it should still read above 12.6. If it does not the battery could be toast.
If it is stalling a lot, and hard to start, you are asking a lot of the battery, and as someone who lives off 12 volts, and has a battery monitor, I must inform you the charging systems on our vans are poor to mediocre at best, with undersized wiring from alternator to battery and an internal voltage regulator which lowers the charging voltage well before the battery wants the voltage lowered. An overcharged battery can be dangerous so they err on the side of caution, and keep the bean counters happy with undersized wiring, and a charging algorithm that favors safety over battery longevity.
You only rent batteries, they are disposable, and it is not in the manufacturer's interest to keep the battery healthy for the longest period of time with adequate charging.
Basically, you cannot rely on your alternator to return much amps into the battery with short drives with a lot of Idling. If you are using a lot of battery amps to start it often, then no doubt you have an amp deficit and are asking too much from it.
If the battery is so depleted it needs a jump start, the alternator will need at least 4 to 6 hours of highway driving, not idling, to bring it up to 80% SOC. That last 20% can take another 4 hours.
A starting battery left at 80% charge or less begins to sulfate which further decreases capacity. The lower the state of charge and the longer it remains low exponentially decreases battery capacity and life.
So remove the battery cables, and make the mating surfaces shine like silver, and make sure the engine to battery ground is clean and tight, as well as the battery to firewall ground, and the engine to frame ground.
While the engine is running the battery voltage should be in the 13.6 to 14.8 range, without the lights or blower motor on. If the battery is fully charged it should fall to 13.2 to 13.6volts, but most likely, right after starting will go to 14.7, and drop after the amps are replaced and the resistance within the battery rises as it fills.
Only after you rule out the battery and grounds should you look elsewhere and throw more parts at it.
Last edited by landyacht318; 04-03-2010 at 05:26 PM..
It's got 173000 miles on it. Don't have tools to check compression. Battery is about 3 - 4 years old. I did test out the tps closed it was .55 and full open was about 4.0 a little low but don't know how many times I've floored it. I checked the crankshaft sensor and that was normal also. Autozone keeps telling me computer but every time I disconnect a sensor the computer registers it right away. So being into computers myself I find it hard to believe that the diagnostic side would be spot on 100% of the time but the firing part of it would be intermittent. It's mainly hard to start after it's been sitting at work all day in the sun. But today it did it when I ran into Autozone for about 10 minutes and later on in the day after I put the brake booster on. I'll check the battery tomorrow. I have noticed the dash board lights a little dim and when it rains the belt squeaks and my gen light comes on. Thanks for all the help. I really appreciate it.
While I'm sure to get stories of batteries lasting 5, 8, and 12 years, most batteries today, made in bulk ,to minimum standards, and are designed to last just past the warranty period.
Ever since walmart started undercutting battery costs of other suppliers by demanding a battery built to a certain price, the manufacturers, US battery or Johnson Controls, have cut a bunch of corners to meet those costs, and all the other shops, Autozone and such have their Duralast batteries made to the same exact, cheap standard by using recycled, thinner lead plates with weaker separators.
If it is 3-4 years old, and now it is hard to start, taking multiple seconds of cranking, and you are relying on the alternator to replace that, it might be time to rent a new battery.
But definitely do the voltage and ground checks. If you've got an old ciggy plug, cut the cable and run that to your DVM so you can see what is going on while you drive it.
When my ECM was failing, I could unplug a sensor and get a code for that sensor, so I don't believe that is a fool proof test. If this began after a rainstorm or two, check to see that the connections to the ECM are clean and dry.