Vapor lock?
 

Hi All,
My '87 L98 auto stalled on me the other day and I was wondering if these cars are prone to vapor lock. I was dropping my wife off at work and setting while she gathered her things and it just stalled. RPM's are normal and the temp was within normal range at @202. I had the ac on. I tried to start it immediately 2 or 3 times but no go. It would fire and stumble but not catch. Tried to listen for the fuel pump each time but surrounding noise was too loud. I let it set for about 30 seconds and tried again to start it and she fired right up as if nothing happened. Ran great the rest of the day. I have started it twice since with no problems but have not driven it any where for fear of being stranded. ......I miss driving it........Could it have been a vapor lock or perhaps trash in the fuel tank, or something more serious? Also I noticed the after I turn the ignition off the pump continues to run for a few seconds and ends with a series of clicks(relay?) from under the hood.Never noticed that before. What do y'all think? Any insight would be greatly appreciated. Cheers

PS: could it be a bad fuel pressure regulator?
PPS: Just looking for some feedback before I break out the .44 cal.universal wrench. I've already got a growing bald spot.

RE: Vapor lock?
 

Hey George...

If you got any jam in yer' fuel lines, it will show if you can do pressure test as recommended in the 'TPI article found" post that I did.

The article said test two ways in the driveway - with vacuum connected, without vacuum connected, and on the road under full throttle. For the third, ya' gotta' get the missus to run alongside with the guage in one hand, and a pencil and paper in the other...

Just kiddin' there; ya' gotta get the guage connected to a 2 foot lenth of line, and tape it to the windshield. It's the only way I've heard of, 'less you got one of them drum roller set-ups in yer' garage...

RE: Vapor lock?
 

Charles, I did a pressure check setting in the driveway not too long ago and it was right on the money. I'll do the full throttle running down the road thing and see what transpires. I'll also check out that artical...I think I saved it. Thanks, George

RE: Vapor lock?
 

Howdy Blueshark, lets just leave the .44 cal.universal wrench in the tool box for the time being.

I would doubt vapor lock, unless you have a fuel line laying against or close to an exhaust pipe. It takes heat to cause vapor lock.

You can do like cwb said and place a fuel pressure guage somewhereso you can watch what the pressure is doing in real time, and especially when it starts acting up.

One other thing, mine did basically the same thing one time. The connection at the MAF sensor had a corroded connection. If that's not connected good, it won't run

RE: Vapor lock?
 

https://www.corvetteforums.com/upfil...DAF97A25E6.jpg

https://www.corvetteforums.com/m_37283/tm.htm

RE: Vapor lock?
 

rshiver,
I Appreciate the reply. I will check the connection at the MAF and do the gage thing when I pick my wife up this evening. I figured they would have engineered the possibility of vapor lock out long ago but you never know. Doesn't hurt to ask, LOL.
These little annoying problems make me want to sell the '87 and finish the BB C3 real quick. All this electronic dooky..... Give me a carburetor and points any day.

RE: Vapor lock?
 

Thanks for the link, Man.....saves me from searchin' the hard drive. Cool! What a country!

RE: Vapor lock?
 

You just described the whole planet:D.

Figure how it is, or pay someone else to rip you off, and NOT fix it.;)

RE: Vapor lock?
 

Or... gut the engine box and install an old school thumper.

And for being ripped of and not fixing it...That's another use for the .44 cal. universal wrench....eh?

RE: Vapor lock?
 

Blueshark, there are actually about 3 things that would make it act as you described. MAF as rshiver said, ignition, and fuel control (which would include injector pulse, fuel supply which would include power to the pump as which there are 2 sources for that, and pump itself). The 2 sources are the fuel pump relay and oil pressure switch which are redundant.

RE: Vapor lock?
 

Hi Mech,
Thanks for jumping in.You had describe a procedure for me to follownot too long ago,to check the fuel system. It all checked out. at that time. You may remember, I was checking because of long cranking times but that turned out to be a dragging starter and worn solenoid.

In the past when it would stall it would not start at all and twice turned out to be the fuel pump and the other was the ECM in the distributor.

Would the relay stop intermittently or just stop altogether? They are printed boards right? not points like they used to be? The pump comes on just like it is supposed to and builds great pressure instantly. Tt holds the pressure while running and increases slightly with susstained acceleration and settles back down.
Is it normal forthe pumpto run-on after the ignition is off? This is a new thing. I always try to pay close attention to my cars but I really don't remember hearing the run-on of the pump before. would the fuel pressure regulator allow this if it were going bad? Also the pressure does bleed down after a short while, after the ignition is off, which I believe is normal, right?

The MAF connection is good butbeing yet another electronic gadget, it could be on it's way out. I need to check this if there is a way. Any tell tails on this one?

This time when it wouldn't start right away it did fire but seemed as though it was lacking fuel. Injector pulse? Guess I need to buy a noid light huh? What size?

The clicking I hear is coming from behind and under the battery. This may be completely seperate from the stall or the run on,but....There is a small contraption down there with several wires attached, what might that be?

Geesh ...sorry it so long here.

RE: Vapor lock?
 

No, fuel pump relays still have the coil and poits setup to handle the amp draw of the fuel pump.



Yes

How quick does it bleed down? Bleed downcan be caused by leaking injector, regulator, or check valve in the pump.

There are 3 relays in that area, but I will have to go and look at my 86 to see what you are talking about.

RE: Vapor lock?
 

The pressure will bleed down in about 20 minutes.

I can't believe I never heard the pump run on before.LOL! Better pay even closer attention than usual,huh? I guessthis car is 20 years old after all.

If the injectors were leaking wouldn't there be smoke and the smell of gas at startup? I get neither of these symptoms. But ....?

The clicking doesn't seem to be coming from the two relays I can see but from under the battery. I didn't notice any down there when I changed the battery out awhile back. just what looks like some sort of distribution contraption down in there. you have to look down in the space behind the battery. ??? It has a post instead of a plug like a relay.

What are the regulators like on the inside.is itsomething likea spring loaded pressure sensitive diaphragm as in an air regulator? Looks like it would be a PITA to change out with my fat fingers, LOL!

RE: Vapor lock?
 

Hi Blueshark, I went out and listened to mine. I really didn't hear a clicking, but I did hear something, sounded more like a small electric motor that ran for about two seconds after I shut the engine off.
I do have one relay directly behind the battery, and Ihave no idea what it's for. And I think I see the "contraption" you're referring to, and it does look like a distribution outlet where the wires go through the firewall.

RE: Vapor lock?
 

Hey rshiver, Thanks for lookin' at yours. I guess the electric motor we hear is the fuel pump. I can hear what sounds like fuel filling the rail as well. Again, I don't remember hearing this before. I'm wondering if my pressure regulator is on it's way out, unless, God forbid, the dang injectors are going bad. But..... like I said, no smoke or smell of fuel at start-up....? No wonder why I like carburetors so much, LOL!

RE: Vapor lock?
 

It's got me curious now, ...It may have been the fuel going through the fuel rail or the fuel going through the pressure regulator.??

Hey Mech...would the fuel pump continue to run until the oil pressure dropped below 4 psi??

RE: Vapor lock?
 

20 minutes bleed off is acceptable, fact, pretty normal. 10 - 20 seconds is not. Have you checked fuel pressure and spark in the sluggish starting condition? No trouble codes I presume? Need at least 25 to 30 lbs of fuel pressure, maintained, for successful starts. Have you checked spark plugs for fouling? If you have a spark checker to check spark, that would be better than a spark plug because it stresses the coil to at least 20 kv.

RE: Vapor lock?
 

Generally, the oil pressure drops pretty quick. The ECM holds the fuel pump relay in for about 2 seconds after it fails to see an ignition signal from the ignition module, which is also a saftey feature ( don't want fuel being pumped into a wreck with a possible fire).

RE: Vapor lock?
 

If you had an injector tester to run an injector balance test, that would certainly help. GM in the late 90's put an injector balance test built into the software of the ECM thatyou could use to run a balance test, but yours is not that new. You might try an injector clean (professionally done) to see if that helps since you can't run a balance test.

RE: Vapor lock?
 

Another thing to watch is your tach when the car stalls and won't start. No tach means possible loss of ignition control since tach signal is derived from pickup coil through the ignition module.

RE: Vapor lock?
 

[ul][*]The fuel pressure is instantly 39psi with key on. Turn it to start and it drops to 38psi and maintains during idle. Snap throttle and it jumps to 41 psi and immediately returns to 38psi. [/ul]
[ul][*]No codes at this time.[/ul]
[ul][*]The plugs look good and only have about 2000 miles on them. I'll get a spark checker as well. Is this checker you speak of the little thingy you put in line with the plug or does it fit over the wire like on a meter.[/ul]
[ul][*]The run-on continues for4 or5 seconds as opposed to 2 seconds and the clicking is a quick series of clicks for maybe 2 seconds almost like what ever it is, is sticking. [/ul]
[ul][*]The other noise I hear from the fuel rail/pressure regulator?, sounds like liquid or a combination of air and liquid being forced at a reasonable pressure thru the lines at a high rate for 4 or 5 seconds, then it slows for just a fraction of a second and abruptly stops. Coincides with the pump run-on.[/ul]
[ul][*]Could the regulator be bleeding air in to the rail? I guess it could be coming from anywhere along the supply line that has a joint as well. I'll have to investigate this thought further.Any in-sites here?[/ul]
[ul][*]What should it cost to have the injectors balance tested by a reputable shop or dealer?[/ul]
[ul][*]Unfortunately I was in a busy parking lot at the time and didn't get to pay attention to the tach. I will certainly watch if it does it again. I hate intermittent problems[/ul]
[ul][*]I drove it last night and today and it ran absolutely perfect. which is scary in it self, LOL, but perfect none the less. I don'tlike being stranded all that much myself , but it's not the end of the world to me as I am kinda use to it once in a while, with all the old cars I have but my wife has a fit if we are stopped somewhere because of the car. Y'all know how that is I'm sure, most women just don't appreciate a classic car and that this is all part of owning them.[/ul]
[ul][*]I really appreciate all the help. Y'all are great folks and this is a great place and I appreciate your time spent addressing my problem. Aren't cars/Vettes great? ....My bald spot is growing. [sm=headbang.gif][/ul]

RE: Vapor lock?
 

Only one thing to do then there George... Keep on drivin' till the problem stays with ya', then you'll have it where ya' want it;)

RE: Vapor lock?
 

That's what I was thinkin'. Never give up. It's frustrateing but this life is short so why sweat the small stuff like bein' stuck in a parking lot. If the parking lot is at a great retauraunt that's even better. When it happens again I'll be ready.

RE: Vapor lock?
 

Well, it died this morning. Went out and started it up, did just fine, fired right up. Pulled it forward so I could get my truck out and it died. Now I can not hear the pump run. Turns over but no start. Pump does not come on at all. What do you all think that loud clicking under the hood was? it was quite loud when it happened. I heard nothing today it just died. I guess I'll start with pulling the pump out and check it with the battery and see if I'm getting power. If it's the dang pump that makesthe third pump in just over a year. Something is up! The clicking has me wondering. It was a quick series of loud clicks. Just didn't sound right. Where exactly is the fuel pump relay located?I'm confused...which ain't hard to do. Cheers

RE: Vapor lock?
 

Hey George... Sounds pretty definitive the pump needs butter (cause it's toast), but make sure before ya' pull it....

I don't think you have to pull the pump to test it, do ya'? Find a place where the pump power lead goes into the tank, put a meter on it and ground the meter negative.

Got power? If so, ya' gotta check to see if it's gettin' grounded (I don't have a clue where the pump ground is - it might be integral with the pump mount, or tank mount). If the ground wire comes back out, then you can test it. Put the (+)on the ground wire, and ground the (-) meter probe to the frame.

Still got power? The pump is probably good - check the fuel pressure again.

If ya' got no power comin' in to the pump, work back to the relay, then further,till you DO find power (and the short)

RE: Vapor lock?
 

Hey Blueshark, on my 85, the FP relay is located on the fire wall, left of the break booster and near the wiper motor. It may be in the same place on yours, I'm not sure though.

RE: Vapor lock?
 

Where are you getting your pump? Autozone? If so, that more than explains it. Stay away from Autocrap parts as they are pure junk.

RE: Vapor lock?
 

Guys, I will check the pump and relay this week end and report back.

The first two were from the dreaded autozone. The last one was genuine GM. But I probably got the only bad one in the state with my luck.

For all I know I could go out there right now and the aggravatin' thing would probably fire right up.

Thanks for the info and replies fellas. Cheers.

RE: Vapor lock?
 

The pump seams fine. I went out this after noon and it fired right up. ran for about 1 minute and stalled. The tach was fine and showed the RPM as it stalled. I tried several more times and it would not start. I looked under the hood and disconnected what I believe is the fuel pump relay. the one on the fire wall just inboard of the break booster. It made a kind of buzzing noise when the car stalled. I unplugged it and tapped on it a few times, plugged it back in and tried to start it again. Started right up and died about a minutes later. I hooked up the fuel pressure gage and tried it again. couldn't hear the fuel pump come on at all. let it set for a few minutes and tried it again. it started and ran for a minute and stalled. I watched the fuel pressure slowly drop and when it reached about 15 lbs it stalled. I found that if I just bumped the ignition but not start it the pump would come on and run for a few seconds and build the pressure up to 42lbs, normal. I bled the pressure off and I did this several times to check the pump. Bumping the ignition would make the pump come on and build pressure and the car would start. If I just held it to start it would not start until the oil pressure got up, and some times would not start at all. Each time I did this the relay that I assume is the pump relay would buzz as if it was sticking. I let the car run for some time and even went for a spin down the road and it never stalled. I noticed the oil pressure each time it would start and it would get to about 6lbs before it would start. Could the relay be sticking and causing it to turn the pump off over riding the redundant oil pressure switch?

RE: Vapor lock?
 

a trick to get you home(beat on the tank with a heavy flashlight or tool for a few seconds) this is not a substitute for a new pump but it a lot of times will get you home rather than being stuck in a parking lot[:@], and yes I have had to do this before;)... but most of the time it works for me to ' limp it home is cheaper than a towing bill':D

RE: Vapor lock?
 

Bypass the relay on pins 30 and 87 to see if it starts or cheaply enough, buy another relay (Delco).

RE: Vapor lock?
 

Installed a new relay and so far so good. Keep your fingers crossed y'all. Thanks for all the help and explanations. You've all been a great help. I'll post back if it turns out different. Cheers

RE: Vapor lock?
 

If the relay fixed that, you still have a problem with the oil pressure relay. You have a dual purpose oil pressure sender/relay that it is a backup for the f/p relay. It is redundant and is under the distributor. It should have a 3 wire hookup on it (a real PIA to get out, have to pull distributor to do it.).

RE: Vapor lock?
 

I was thinking about that. and was wondering if the relay sticking or fluttering would over ride that and cause it not to come into play. Can you get to it from underneath the car?

Also the lead from the O2 sensor was lying on the heat shield of the Cat Cnv. and the insulation was melted, I rerouted the wire and and wrapped the bare spot. would it shorting to the Cat. Cnv. cause any problems like that?

RE: Vapor lock?
 

It sounds like the car was just relying on the relay and the oil pressure switch is not working. No, the switch is under the distributor.


Yes, it would short to ground and make the car go full rich. Any black smoke @ idle?

RE: Vapor lock?
 

[:@] I figured that was the only way to get to it butthought I'd ask anyway, LOL!

I didn't notice any black smoke but I had noticed some black soot in the tail pipe as of late, so.....? It may be just me but it seems to run a little beter since I rerouted the wire. :DIdels smoother and a slight bit better exceleration.

Thanks again for the help, LB I really appreciate you takeing the time to address my questions. Don't know if I can, but if I can ever help you .......

RE: Vapor lock?
 

N/P, just build a me a free boat! LOL.

RE: Vapor lock?
 

Sounds fair to me. :D

RE: Vapor lock?
 

How 'bout one like this? I call it the "Wette Vette". 60hp OB = 65mph+.

[IMG]local://upfiles/2713/99B4E000AC1C4F7A92822C5E8B647B64.jpg[/IMG]



Notice the '74 Stingray in the back.