Car almost dies after spirited driving

[silasmoon]

Zinz, I had the same thought. This isn't really a fuel starving situation to me - classic fuel starving usually gets people in the high-rpms / highway cruising. The fuel filter is clean and I've put over 1,000 miles on the new engine. The timing could be what's up. 

I set a curve in the 123 so that at 2,200 RPMs the engine should be 25 degrees advanced. With the vacuum on the carb plugged, and some tape over the 123 dizzy advance, I had a friend hold the car at 2,200 RPMs. I placed the timing light on Cylinder 1 spark plug cable and timed it to the BB in the window (25 degrees BTDC), to guarantee that the curve in 123 and the engine were in sync. That's how I assessed the distributor as having no static advance. Then I programmed my own, new, curve based off of a Ti curve. That curve is pictured below. 

At idle the vacuum advance doesn't take effect (only above 1,500 rpms). The curve shows the car sitting at about 18-20 degrees BTDC at a 850 - 1,000 RPM idle. 

Attached are my curve, vacuum curve and two reading with the car at idle. 

Edited April 24, 2017 by silasmoon

[silasmoon]

Called my guy today and he said it was a 3-5 PSI fuel pump, and thought perhaps we could try just putting in a simple inline pressure regulator for the time being. I guess any old would should do it? 

[silasmoon]

Went ahead and ordered this fuel pressure regulator. I will let you know how it goes. 

[zinz]

The adjustable Mr Gasket regulator is what I've used on a couple cars.  It comes with a variety of fittings and found at many box auto parts stores.  (make sure it's the adjustable one)

 

 

Your 123 curves don't draw any flags with me... it should run fine with those numbers.

 

 Ed

 

 

[zinz]

That Petrol King will work just fine. It's adjustable and should hopefully solve your problem.  

 

I might suggest adding this one-way valve near the tank as well.  I've found that it helps keep the line full of fuel for quick restarting.

 

Good luck!

 

Ed

Edited April 25, 2017 by zinz

[silasmoon]

Minor update - I am still waiting on the fuel pressure regulator, but I have noticed that when it almost dies it's when I really stab the brakes such as when I am coming off a freeway onramp. I don't think its the break booster though, as when I have the car idling and stab the brakes it doesn't change anything. 

I also notice that right before it happens the check oil light will come on and then go out when I feed it a bit more gas. Oil levels are good though. I checked the cable from the coil to the distributor and all the coil connections. One odd ball thing I noticed was that one of the wires inside of my Momo steering wheel had come loose and the horn was only working some of the time. I patched it today. 

Otherwise it's been happening a lot more recently, even though I upped the idle speed screw a smidge so it idles at 1,000 rpms now. 

[KFunk]

On 4/24/2017 at 10:03 AM, KFunk said:

what about vapor lock?  You know, when it gets hot and vaporizes fuel in the line, and the bubble prevents actual fuel from reaching the engine.  This would be more of a problem on hotter days, and usually occurs when you slow down and decrease air flow over and around the engine.    

 

How thick of a gasket do you have between the carb and intake manifold?  Is the fuel line fully protected from any heat sources?  Any other cooling issues with car?

 

[jmiller]

I had a somewhat similar problem when playing around with my new 123 distributor.  Car would sputter when pulling up quickly to a stop.  I figured it had something to do with my settings, therefore a timing problem.  I think the advance setting at high vacuum (0 degrees, similar to yours) was retarding the timing too much, lowering the rpm, which then went to the bottom of the advance curve, ending up with 0 degrees advance (similar to your curve).  So I reset the vacuum advance to max at 0 kP and set it to kick in above 400 rpm.  Problem solved!  This may not be your problem, but I thought to mention it as something to check.

 

[silasmoon]

Interesting, so your settings would be like:

kP / Degrees
0 / 7.0
75 / 7.0

200 / 0

@400 RPM? I did remove the vacuum hose from the distributor last night to see if it had to do with a vacuum leak / vacuum advance issue and I got the same thing, but I am willing to try it. I started noticing the problem after I adjusted the timing on my distributor slightly. The funny thing is the Android bluetooth app is SO BAD that I can't even touch the vacuum curve likely. 

 

[silasmoon]

I don't think it's vapor lock @KFunk although I've been wrong before. I live in Northern California where the weather has been mid 50's to 60's. The temp gauge in the car never gets above the 1/2 way point ever and the fuel lines aren't resting on the engine or anything. I do have both a thermal visualizer (FLIR) and a laser thermometer though I can use to check. 

[silasmoon]

My other thought is that there is some vacuum issue with the tank now that I have an electric fuel pump. The length of the fuel line attached to the return line is capped in my engine bay. It's still attached at the tank. I have a breather line from the filler neck to the white catch canister in my trunk though as it's a 76. I deleted the smog equipment and a very tired looking charcoal canister long ago. 

[KFunk]

3 hours ago, silasmoon said:

I don't think it's vapor lock @KFunk although I've been wrong before. I live in Northern California where the weather has been mid 50's to 60's. The temp gauge in the car never gets above the 1/2 way point ever and the fuel lines aren't resting on the engine or anything. I do have both a thermal visualizer (FLIR) and a laser thermometer though I can use to check. 

 

Again, how thick is gasket under carb?  Some people use a thick spacer for this very reason.  Your fuel pump is in the engine bay as well next to the engine.  Myself, and many others, keep theirs in the back near the gas tank.  Your temp guage doesn't matter too much, although it could lead to that problem as well if you had a cooling problem.  

 

Today's fuel has 10% ethanol, and some say that it has a higher vapor pressure that leads to more vapor locking.  It's arguable, but the mix is different.  I have vapor lock all the time on my completely stock lawnmower built in the 90s.  I had to take off the fenders to get better cooling, and then just put an electric motor in the back of the mower to remedy it.  My truck also vapor locks quite a bit, but it does have a mechanical pump and the carb sitting on the exhaust.  That's the stock setup though which must've been fine in the 60s, but apparently not now.  On hot days I just have to crank it a little longer to push the vapor out.  

Edited April 27, 2017 by KFunk

[silasmoon]

All fair and good points. I went out to the car today and couldn't even get it to start. I noticed that the choke was slightly open. I added some more tension to the choke spring and loosened the choke butterfly screw so that the choke plates would fully seal the carb. Still wouldn't start. Perhaps the float needle is sticking? 

During all that my #@$*@# passenger door lock cylinder also pulled out and snapped, so I had to take a break before I torched the car. 

 

[Simeon]

44 minutes ago, silasmoon said:

All fair and good points. I went out to the car today and couldn't even get it to start. I noticed that the choke was slightly open. I added some more tension to the choke spring and loosened the choke butterfly screw so that the choke plates would fully seal the carb. Still wouldn't start. Perhaps the float needle is sticking? 

During all that my #@$*@# passenger door lock cylinder also pulled out and snapped, so I had to take a break before I torched the car. 

 

 

Hang in there. Some days are like that. Eventually you work through everything on the car and then it's like maintaining a modern car. We are fighting against a combination of 40 years of misuse and well meaning but flawed modification. 

[silasmoon]

Minor update, got the fuel pressure regulator in today, but realized it has no markings in regards to PSI setting. How do you folks set it? I noticed that it took 20 turns to take the adjustment screw from lightest pressure to strongest pressure. It puts out 5 PSI so each full turn represents 1/4 PSI? I don't think that's scientific enough, and I will likely need an inline gauge as well. 

Additionally, regarding mounting all the new hardware, I thought I might mount it to the washer bottle holder with an L bracket. Any reason why I shouldn't do that?