Any car guys that can help? – Why is my car vapor locking?

S

SAK

Joined
Sep 28, 2001
Messages
508
…or at least I think it is a vapor lock problem. Can anyone help diagnose the problems with my OLD friend?

I have a 1988 Pontiac 6000 (similar to a Chevrolet Celebrity) with a 2.5L 4-cyl engine. The car has 170k miles on it and I am the original owner. It runs fine except for this single problem.

SYMPTOMS
- One night, while driving for at least 20 minutes of stop-and-go driving at a maximum speed of 5 miles per hour, it totally died. Cranking and cranking obtained nothing. Waiting 15 minutes did nothing. Then I cracked open the fuel line where it connects to the carburetor, let some foamy fuel run out, and re-connected. Then it started right up.

- Today, it started up just fine (instantly) and I drove it for about 4 miles and then parked it. 10 minutes later I tried to re-start it and it cranked and cranked but it did not even want to consider starting. Waiting another 5 minutes didn’t help.
I waited 3 hours and tried again and it started up instantly.


If it helps with diagnosis: sometimes it sits for a long period of time without being driven (3 weeks to 3 months).

Can anyone offer suggestions on how to fix this? I know the car is old, and has a lot of miles, but she is like an old friend and I don’t want to get rid of her. She runs well other than this. The problem is if I just go replacing parts willy-nilly, or take it to a mechanic, the repair costs quickly exceed her blue book value.

Thanks for any help,

--SAK
 
Bad gas would be a good place to start. In 2 weeks, gasoline can degrade to a point where some motors won't burn it properly (I had a dirt bike like that). Gas that has been sitting for 3 months needs to be drained and replaced unless you use a storage additive. I'm not a mechanic, so take this with a grain of salt...:)
 
Hi Cougar and locomike,

The gas probably has been setting for close to 3 months (in a garage). Would bad gas cause the situation where it would start instantly when cold (and other times) and then not start AT ALL other times?

It runs fine when running, it just has the binary problem where sometimes it starts perfectly and sometimes not at all. When it doesn't start it is cured by cracking the line or waiting a few hours.

Thanks for the quick responses.

--SAK
 
try changing the fuel filter first- doesnt sound right that you have to relieve line pressure before it will start --

also do you know how to jump read the computer?
find the computer plug under the front of the dash,jump from 2 pin holes(use a paper clip) with key on (some its the outside 2 pins sometimes inside -either way you wont hurt anything) and watch the engine light-it will flash-flash's fast and slow-2 slow and 4 fast is a 24 code ect ect- if it has more than 2 codes one for its started one for its finished,deterime what codes it reads-it will help find the general area of the problem-you can get the codes online or at napa
 
your problem could be bad or old gas. There is a fuel additive called Staybill. Not forsure of the spelling. I think I saw it at Wallmart and can be found at your local lawn mower repair shop. The staybill prevents the fuel from breaking down if the car sits for extended time. How long since you have changed your fuel filter? If you can't remember or its been over a year or two ; then you might want to consider changeing it out. I am not for sure, but I think the filter will be inside the frame on the drivers side. (someone please correct me if I am wrong on this particular car) I just changed out the fuel pump on my older chevey truck. It would start great when cold, but after running for an hour or so would then refuse to start for a few hours. I have a buddy who is a G. M. Mechanic at a dealership close to me. He plugged the computer into my truck and it spit out a code that indicated low fuel pressure. After I changed the fuel pump no more trouble at all. The pump is located in the fuel tank. Removeing the tank can be somewhat of a job. You have to remove the filler neck too so the tank can be dropped down for repair. There is a screen located inside the tank too. That will most likely need to be changed out too. I think my screen was like 13 bucks or so at local parts chain store. It is much easier to do when the tank is 1/4 or less full. If you feel this is a bigger job than you can handle ; the prices for changeing out the pump can be kinda high.You might just need a clean tank of fuel and or a new fuel filter. Please forgive if I ranted on too much. Good luck!
 
I would drain the fuel lines, change the filter, and add Sta-Bil to the tank afterwards. Bad gas that has been sitting can leave deposits within the filter causing a blockage. I had this same problem with a 1988 Ford Tempo. Draining the tank and cleaning the line plus a new filter and pump solved the problem.
 
I had an '86 6000LE.

Had very very similar problems, and it took almost a week for the best troubleshooter I know to come up with the problem.

There is a coil located in the "distributor". Mine was "old" & cracked (1994), and it would drive a while, then stop. Wait, nothing. Wait longer, fine. Almost like a heat short.

Replaced it, and sold it about 1K miles later. No problems afterwards.

Have your mechanic check that.
 
I don't know the car, coz I'm a foreigner, but if it has a manual fuel pump rather than an electric fuel pump, remove the top and check if there is a small tear in the pump diaphram.

My sis in law has a Pontiac Sunbird. Very reliable
 
Your gas is too old, and has lost it volitility, causing your car to stall out when warm. Cold fuel is more volitile (SP?), so it runs fine until it gets the fuel lines warm, and warms the gas.

The above recommendations are solid; drain your old fuel out, change the fuel filter, refill with new fuel, and ad Sta-bil, or some stuff from NAPA called Seafoam.

Also, I think your car has Throttle Body Injection; looks like a carburetor, but is actually a big fuel injector.
 
sure could be the gas, i doubt its vapor locking, thats more of a carburetor thing and not real common with them imho.
 
Locomike, Cougar, Rosconey2, Jay, KV, thatmguy, Andrew, Code3 and SIFU1a - Thanks. I appreciate the good information and the time you took to type up replies. I am sure you have saved me money by giving me suggestions on where to start addressing this issue. As a result, I am upgrading my just-expired gold membership to platinum to help give back to the community.

OK - Enough with the mushy stuff.

I did two more checks yesterday to see if this was repeatable – it was. I drove for 5 minutes (the car ran fine) shut the car off, waited 2 minutes and tried it again and it would not start. After waiting and hour or so and trying again it started right up.

I will start working on this today.

Of course the gas tank does not have a drain plug (that would make this too easy). It also has an anti-theft design to make siphoning out through the fill hole impossible. One manual that I read suggested trying to siphon it out through the line coming from the fuel pump. I am thinking about disconnecting the line at the fuel filter and adding a short section of tube so I can get below the level of the tank and then running the fuel pump long enough to get flow started. Not sure if that will work but I figure it is worth a try to avoid a mouth full of gas.

Thatmguy, was your 6000LE a 4 cyl or a 6 cyl? If correcting fuel related issues does not address the problem I will look into the coil. I just wondered if you had the same engine that I do?

Jay, you are correct. The fuel filter is on the driver’s side behind the rear wheel. And you definitely did not “rant on” too much. The more information - the better.

Code3, you are correct. My car does have Throttle Body Injection – good catch. Thanks for tactfully pointing that out.

Thanks again,

--SAK
 
Man, it has been 12 years since I sold it.

I think it was a 4-cyl.:confused: :confused:

Sorry, killed too many brain cells since...
 
IIRC the last car in the US w/a carb was a yugo in around '82 or so, emmision problems spelled there demise.

a yugo, now thats a fine automobile lol.
 
Hey Guys..

Not sure if this has been said or not,, but you may try changing the gas cap..
Not sure why,,but sometimes this causes problems.. either it's plugged and can't breath or it's leaking...

ttyle

Eric...
 
Since it has 170K the engine probably has built up dirt and grease and is getting too hot and needs to be cleaned if that is what is causing vapor lock and that is the problem. You might try a length of gas line hose split lengthwise and cover the metel gas line above the engine to prevent the gas line from getting to hot.

sog
 
My ex has a '94 Taurus 3.8 V6 with a similar problem, but only occurs on hot days with a/c on. At first I thought vapor lock as well, gas quality was good..and the temperature gauge denies coolant over heating..
We haven't been able to solve problem as it is sporadic.. but was given the explanation by one mechanic of over heating of the old in tank fuel pump. This is due to hot fuel being used as a coolant for pump. He mentioned a Tempo they managed to replicate this on, they could see the fuel pressure drop as heat built up.
My reg. mechanic had never heard of this one, and posited either an old coil or a module over heating and stopping functioning.
Has anyone else heard of this particular fuel pump problem? So far we haven't chosen any of the $500 worth of options.
cheers
 
There have been some good suggestions pertaining to both fuel AND electrical. (I was a cycle mechanic in my previous life) This is not symptomatic of bad gas. It's too sporatic.

Start by isolating the problem. Fuel or ignition? You need to get to the point where it doesn't run. (Always the dilema. Failure on demand isn't always that easy.)

Find the air inlet or a spot where you can spray some starting fluid (ether) in there. Just a 2-3 second squirt. This stuff is very effective, but has a danger potential. Be careful.

Bottom line: Spray a few shots in the air ducts and then try to start it. If it fires for 1-2 seconds, then it is starving for fuel. No difference? Look at an overheated ignition component.

It may fire and still be electrical. The overheated electrical component may be the fuel pump. The plot thickens...

Coop
 
Check your fuel line for places where it might get too hot. If hot the gas boils and then you don't get a good flow.


Paul
 
my father had a similar problem w/ a saab. the fuel pump would foam the fuel and then the car would stall if you accelerated too fast or started the car after you had just stopped it
 
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