Car dying, don't know why

[pparaska]

This is weird. I can be driving along, either after just cruising or really getting on the throttle, and it will act like it is running out of fuel. The pump is still running (believe me I can hear it!) and I have pressure and there's fuel in the bowl because when I get out, and tap the throttle I can see lots of fuel squirting out of the accel pump squirter.

 

Weird. I guess it might be electrical (ignition) but it seems more carb related. It doesn't cut out completely, but there's NO power and it will finally just stop running.

 

After a few minutes I can get it to start again and it will work fine for either a week or 5 minutes. No pattern as to high underhood heat, ambient temps, fuel (did it on different tanks of gas), nothing.

 

The setup is my 327, double hump heads

-750 vac sec (sorry guys, the 600 just had NO guts)

-Holley 300-36 dual plane with blocked exhaust crossover

-Holley blue pump with regulator on firewall

-GM HEI with blue streak module and Thunder something coil

- #12 wire running to relay next to HEI for coil/distrib power, distrib grounded at firewall, grounds in car are extensive

 

Any ideas appreciated.

[Dave]

Pete I was having a similar problem with a Mallory Unilite a couple years ago. It turned out to be a noisy voltage supply to the ignition. The cure was a 20 amp stereo filter (a rather large capacitor) from Radio Shack. On your car it needs to be installed before the ignition relay because the filter holds enough power that the car will run on for a moment after it is shut off. http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F002%5F001%5F019%5F008&product%5Fid=27%2D055

[John Scott]

Just throwing out an idea. I had a coil which caused an intermittent dying problem, loss of power. Good healthy spark sometimes, but eventually got bad enough to diagnose and replace. So rare to have a coil go I disregarded it at first since it would throw a good spark. After dying it would be really weak. Good luck,

John

[Kevin Shasteen]

Originally posted by pparaska.., it will act like it is running out of fuel.., and there's fuel in the bowl because.., I can see lots of fuel squirting out of the accel pump squirter.., I guess it might be electrical.., It doesn't cut out completely, but there's NO power and it will finally just stop running.[/QB]

Pete,

 

When you say it "Feels like it is running out of Power" are there any backfires or is the "Running our of Power" a quiet loss, as in a loss of power without any backfires? Ex: loss of power if/when a Fuel Filter is clogged, (No Power at High Rpm's only Low Rpm's).

 

And when you say you dont think it is fuel starvation, does it smell like there is excessive fuel at the carb?

 

Do you recal what the "Ambient Temp's", of the day were, specifically at the moment when you experienced your "loss of power"? The reason I asked is this, if it is ignition related, and I'm assuming your ignition is a "Hot" set up; if that ignition doesnt get enough "Ram Air" it could overheat. Throw out the possibility of a bad ground supplementing the hot ignition...which could cause a heat soak condition????

 

Just throwing out ideas; but if you would, please elaborate on if you could/could not smell excessive fuel at the carb. If you could smell excessive fuel I would argue that your problem was a "No Spark" or "Not Enough Spark" scenario. Also, please elaborate on if you did/did not experience any "backfires" when your loss of power manifested.

 

Kevin,

(Yea,Still an Inliner)

[pparaska]

Here's a blow by blow response, Kevin:

Originally posted by Kevin Shasteen:

When you say it "Feels like it is running out of Power" are there any backfires or is the "Running our of Power" a quiet loss, as in a loss of power without any backfires? Ex: loss of power if/when a Fuel Filter is clogged, (No Power at High Rpm's only Low Rpm's).

No backfires. Quiet power loss. It seems to kind of want to run, but has no power and then just dies even with the clutch in.

 

It's like the carb has run dry of fuel. But it's full.

 

And when you say you dont think it is fuel starvation, does it smell like there is excessive fuel at the carb?

There's hardly anytime that there's not a smell of excessive fuel with the 750 vac sec on there. Although 3/32" holes in the primary throttle plates have allowed me to get the blades closed enough so that too much of the transfer slot is not showing and it's leaned the idle CONSIDERABLY. Much better now. I still have an off cruise stumble (goes for a split sec, then coughs, then goes hard from there). I'd tried jetting up from 68 to 73s, gone with 28, 31, 35, and 40 squirter nozzles, now at 25 and it still does it. 73 jets were rich and 70s seem pretty decent, but it's by no means dialed in.

 

Do you recal what the "Ambient Temp's", of the day were, specifically at the moment when you experienced your "loss of power"? The reason I asked is this, if it is ignition related, and I'm assuming your ignition is a "Hot" set up; if that ignition doesnt get enough "Ram Air" it could overheat. Throw out the possibility of a bad ground supplementing the hot ignition...which could cause a heat soak condition????

It's was about 80-85 the last too times, and the car had sat for 20 minutes before. Under hood temps seemed much lower than other times when it had not done this. I have grounded the distributor with another wire that goes to the firewall as well.

 

Just throwing out ideas; but if you would, please elaborate on if you could/could not smell excessive fuel at the carb. If you could smell excessive fuel I would argue that your problem was a "No Spark" or "Not Enough Spark" scenario.

Well, not really. I did notice a fog of fuel rising out of the primaries though, on the last ocassions. But it might do that everytime I shut it down, I don't know.

 

Also, please elaborate on if you did/did not experience any "backfires" when your loss of power manifested.

No backfires.

 

Thanks for all the help guys!

[pparaska]

Thanks for that tip Dave.

 

Just wondering. Any chance that my stand alone MSD soft touch rev limiter is hosing things up? I disconnected it, but it will be tough determining what the problem is since it is so unpredictable. One indication is that the car died twice in about a mile of mild driving last night (right before I posted this), and the second time I pulled the distrib cap to take a look (everything looked fine). I saw the two connectors for the rev limiter that I had spade terminals in, so I unhooked it hoping to do ANYTHING to get me home. It ran fine all the way home (about 30 miles).

[Mike kZ]

I had a 41 Chevy street rod, with a 650 double pumper that would every once and awile die. I took the carb appart and found a small piece of plastic film in the bowl that occasionally laid over the jets and starve the engine. How this piece of film got in there I have no idea. Did you check in your carb?

[Guest greimann]

When I ran a carburetor, on warm days the fuel would boil in the bowls and stall the car out. There were no fumes or vapors when I popped the hood to check, because the boiling immediately stopped. I solved my problem by going TBI. You may want to test this theory on your car by running without a hood.

 

Also, youre stumbling problem sounds like a timing issue. Advance a couple of degrees and see how it runs.

[Pop N Wood]

My first thought was dirt in the carb also. Along the same lines it could be a sticky float/needle valve. If it was a vapor lock condition then it would be more correlated with the under hood temps.

 

But a bad spark will do the same thing. I do not know how you tell an intermittent loss of spark from an intermittent loss of fuel. Did the problem occur with the 600?

[Kevin Shasteen]

Originally posted by Jim Powers: Did the problem occur with the 600?

How you tell an intermittant loss of fuel -vs- intermittant loss of ignition is you will get an excessive smell of fuel and an occational backfire whereas with the intermittant loss of ignition. For an intermittant loss of fuel you will get a quiet loss of power (No Fuel-no source to Ignite/and no excessive smell of fuel). Without an intermittant loss of fuel your car will also lunge and jerk-may even spit or sputter a little, but usually [yes "usually"] you wont notice any backfiring. This doesnt mean that it any easier to diagnose...there is a fine line between the symptoms and requires a close monitoring of the situation if/when it manifests itself.

 

Pete,

 

My next suggestion was going to be to put the 600cfm carb back on and see if the problem occurs; then if it does not you will know that the problem lies somewhere in the application of the 750...be it tuning, excessive fuel-whatever. I would try a different carb just, if for no other reason, to eliminate or finger the carb as the possible problem.

 

I once had a 66 Olds Cutlass (Bone Stock) 330V8 Police Interceptor engine that experienced loss of power similar to what you described. As I removed the carb I found that the base plate gasket had torn and the part that tore had finangled its way into blocking two of the Venturi. It had become a hinderance to airflow; as you know-this airflow at that part of the carb is the main signal that pulls the fuel out from the bowls. So even tho my carb was not running out of fuel....MY ENGINE WAS RUNNING OUT OF FUEL due to an improper booster signal.

 

Keep us apprised of any/all diagnosis along the way and keep picking our brains. You and the rest of us should be able to solve this grimlin.

 

Kevin,

(Yea,Still an Inliner)

[pparaska]

Thanks for the help guys!

 

No, no dirt in the carb. I have it apart almost daily . Ugh.

 

The needle and seat was fine when it did this and I pulled it out right there on the side of the road. No dirt, and no sticking. the fuel level in the bowl was fine too. I pulled the bowl yesterday to do a jet swap and it was all clean in the bowl, and that side of the metering plate.

 

I'm beginning to wonder about vapor lock. But I agree it doesn't seem to make sense that it doesn't do this more often when it's hotter out.

 

I'm thinking about a gasket/heat-sheild/gasket arrangement under the carb now. I don't have much room for stuff between the carb and manifold, so it will most likely be a custom job.

 

In the mean time, Dave, I think I'll try popping the hood and letting the safety latch catch it, allowing it to only raise up and inch or so.

 

I'm sure the gaskets are fine - I'm super careful when working on the carb and I double check stuff like that - I've been burned by that stuff before too! And I have a perimiter type carb to manifold gasket on, so that couldnt' be blocking it.

 

I may do what you said, Kevin and try the 600. Or I may just wait until the 650 DP gets on the car.

[pparaska]

I didn't fix the hesitation problem, but I did something I've been ignoring for a while - LIKE A DUMB$#!T !!!! :

 

I checked the mechanical advance curve in the distrib! Ross had mentioned a while ago that it sounded like not enough advance. So I bumped it from the 10 I started with to 14 BTDC like he suggested.

 

Well, alot of people know that's not a good way to do a timing setup. Since this distributor had been dialed in on a machine years ago by a now defunct speedshop, it was NOT like a stock distributor, so 10-14 degrees BTDC at idle (with the vacuum plugged, of course) was not enough. With it set to 14 degrees at idle (800 rpm and lower actually), it maxed out a 2400 rpm to only 31 degrees or so.

 

So I bumped it to 38 and went for a drive. Holy Moley! There must have been another 20-30 hp there! No, I haven't even hooked up the Road Dyno yet, but the timing and carb are getting in the ball park of where I need to start doing performance tuning using it.

 

I did a roll on throttle mash in third gear at about 50mph. Woah, felt quick to me. Chirped 4th gear without powershifting, just shifting a bit fast and hammering the pedal back to the floor when I let out the clutch. I really need to hook that Road Dyno up to see what kind of performance (heck, just rpm versus time logging could yield 0-60, 50-100 times!)

 

Oh. I need to put the inner valve springs in. I've been not revving past 5000 rpm. That recent Car Craft? article about low and mid range increases in torque with stiffer valve springs on the Comp Cams Xtreme cam makes me think I really need to do this soon. The motor has 500 miles on it anyway. I'll be putting the springs in this week and probably going to Mobil 1 oil. Is it too soon for the Synthetic?

 

So Ross, and then Dave today - thanks for the jab to finally get me to check the total timing. Damn, I feel stupid....

 

BTW, the 650 should be here this weekend or beginning of next week. I can't wait. The 750 works well 99% of the time. but low to low-mid rpm off cruise stumble is still there. I tried a 28 squirter and it's still a big hole there.

 

Having lots of fun driving it lately guys!

[blueovalz]

Pete, this was very amusing because just last week I was going through the same thing. I did the "drill the hole in the throttle plates" routine, and still, no response to my idle adjustment screws because too much of the slot was uncovered. Anyway, the car seemed OK, but I bumped up the timing because it "felt" too retarded. DAMN, just like your experience, I had gobs more HP. Anyway, I could now adjust the throttle plates back to almost a closed position now, the idle adjustment is almost normal, and with the additional change from a 69 primary jet to a 71, it cruises soooo much better and smoother, with a much better transition to WOT. I had to laugh when I saw your posting tonight. I would have mentioned my experience to you earlier in the week, but thought for sure you would have the correct timing (silly me). Now I'm going to go back and see if that #25 squirter will work better than my #40.

[pparaska]

Terry, you assumed I wasn't a fool and thought I'd already done the CORRECT thing, that is checked and set total timing. I ain't that smart and performance tuning is pretty much all new to me since I've not really done anything like this in 20 years.

 

I agree - I need to get the timing dialed in (the adjustable vacuum can too) and then go to the 650DP and start all over. I guess I need to get a few virgin throttle plates for the 750 vac sec before I put it on Ebay. I'm hoping I can get away with no holes in the throttle plates on the 650. If they're too big, then small changes in load (like the cooling fan coming on) at idle plays havok with the idle speed.

 

I've got ALOT to learn about performance tuning. I've been researching tunig a bit and I knew getting the timing in the ballpark was the first thing to do, but thought setting it to 14 or so initial was close enough - WRONG - especially if you your distributor has less than stock maximum mechanical advance.

 

BTW, on my motor, the 40 squirter was WAY too big. Big clouds of unburnt fuel behind the car when I shifted and put the pedal down, even in "regular" driving.

[660Z]

hey guys,

the main thing about performance tuning is don`t get too technical and over think things.the best tool you`ll ever own is the seat of your pants!...ALL cars have a different personality and just becausle it sayz it in a book dosen`t mean it`s right.....and don`t always trust your insterments either just use them as referance...i once tried getting technical and relied on a timming light instead of my senses turns out the brandname light was way wrong in the area i wanted it to work!....never again!...my uncle has a 11 sec motor running 13`s...overthinks everything and just won`t listen!!! he`s put 4 cams in and swears their ALL ground wrong #1 open in #6 position (180 deg. out)i`ll tell you what`s out is he`s dial in`s!...relies on a manual for a STOCK motor...performance are not stock settings!

 

remember use your senses you`ll learn a lot more.

 

oh and about the cams....with computers and quality control the way they are now dot to dot (sbc)are 99.0% what the cam card sayz anyway...my uncle refuses to put it dot to dot!!!....mark

[pparaska]

FINALLY found it!

 

It only happened another 5 or six times in the past several months, but today it happened TWICE!

 

I was giving rides to a local guy (ITS Z racer) and his two man pit crew . First the racer was riding with me and the second time I went through the gears at WOT, it happened at about 5500 rpm.

Pulled over, and after a few times cranking it started up. Though it was because the tank was 1/4 full, so we went an filled up.

 

Next I was giving on of the pit crew guys a ride and it happened the first time I got into it.

This time it didn't want to start. Electric, Blue Holley pumpe was making the right noises. Then he notices the fuel pressure gage was on zero while I had the pump on and trying to start. So I left the pump on, got out a screw driver and started tapping on the POS Holley fuel pressure regulator. Slowly the pressure goes from 0 to 6psi, where I had it set. This is the second one of these I've had on the car. The first one would fluctuate and not hold a constant pressure from one day to the next.

 

Problem solved. POS Holley regulator!!!!

I should have gone with the Mallory bypassing regulator. No matter, the Holley blue pump and POS regulator is coming out whenever I get around to putting the TBI system on.

 

BTW, the ITS racer is now talking about forgetting about the L6 for his street Z and going with a V8 for sure. It seems him and his pit crew buddies really like the flat torque curve that starts just above idle That and getting pushed back in the seat a lot more than the NA L6s they use in the ITS car

[pparaska]

(Bumping for those of us that look only at "today's posts")

[blueovalz]

Holy Conversion BatPete! An ITS convert? This ones for the books. Glad you found the problem being I've got one of those Holley Blue regulators in the back of my car. I don't know if this is the POS model or not though. Is there any special markings for that?

[Mikelly]

Nothing like being a bad influence! Pete, I had the same problem with my Holley regulator, and it stayed even with the Mallory unit. I even swapped pumps... Three of them, and two regulators. Going FI is the only way to fly!

Mike

[denny411]

You would think a reputable company such as Holly would monitor the quality of there regulators a little more closely. That is a potentially serious problem if you are running nitrous,turbo or a supercharger.