• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Need Help before I lose my mind

Share this page

jcatnite

jcatnite

Jedi Knight
Offline
Any suggestions are welcome, I have chased this thing around and around and still haven't caught it. I have a 76 with a 1500 that just won't idle for very long. I keep thinking I got it and then it goes and starts acting up again.
Here are the specifics,
High compression 1500 with rebuild 4K miles ago. It has a fast road kent cam kit, new pistons, head job by reputable machine shop, cylinders bored 0.030" over, crank turned 0.010: under, new bearings (of course), new timing chain and tensioner, new timing gears, new water pump & new oil pump. The cam has been dialed in to Kent's specs, and verified a couple more times post installation. (I think it is max lift at 106 degrees).

Since the rebuild, I've installed a weber DGEV on cannon intake, a rebuilt 45D distributer with pertronix tuned by Jeff Schlemmer for my engine specs, new coil(non balast), new plugs and wires, a pacesetter header and 1 7/8" exhaust.

Jeff said to set the timing at 14 degrees BTC but it runs a little better around 18 BTC. (It did before the rebuild too). I can't verify intake vacuum as the manifold has no provisions for it.

I can set the idle at 900rpm with the mixture screw at 1 1/4 to 1 3/4 turns from seated and the idle speed screw at 1 1/2 turns in. Every thing is great for a while but after driving it for a few minutes any extended idle over 3 to 4 minutes and the engine begins to stumble. The pedal is very fluffy and requires some pumping to recover the engine. (Like the carb is loading up but leaning it out has no positive affect) It is worse when it is hot but the engine temp is a solid 180 no matter how long I idle. (verified with infared temp sensor on return hose) The car has lots of power in the power band and is quick off idle as long as the carb is kept cleaned out. When you remove pedal after WOT it bounces back to about 1400rpm and then slowly settles down to 900rpm. I've checked and checked for vacuum leaks (anyone use propane?). I am at my wits end and don't know where to turn next. Increasing the idle to around 1300rpm helps some but it still starts to stumble just not as bad.
On the weber, I've lowerd the float level 1mm then a 2nd in an attempt to isolate the problem. The crankcase is vented to the air cleaner through the valve cover.
I'll take all suggestions in short of giving the car away. It can idle I know it, just not sure how to convice it....lol
JC
 
Sorry, should have mentioned that. I have an electric fuel pump mounted on the firewall that puts out 4psi. I have the Holley regulator after the fuel pump set to 2 psi. I have tried various pressures from 1.5 to 3.5. The results are pretty much always the same regardless of the pressure.
Very good question I chased that rabbit way down that hole.
Thanks,
JC
 
Your fuel pump may be mounted to high. It really should be near the tank.
 
Spray some WD-40 all around the intake while the engine's running to see if you have vacuum leaks.
 
I had planned to move the fuel pump back near the tank when I strip the tub for restoration.
As far as the vacuum leaks..it is always possible. But I've tightened the intake a couple of times (had to make a wrench now it is easy) and have sprayed, carb cleaner, and starting fluid at suspect places. Only "rise" was around the butterfly shaft but it was only a possible as I couldn't repeat it.
I may need to ship it to Doc...lol. The body is rough but I plan to bring it to tip top shape after engine is finished. When I do pull it, I will tap the intake for a vacuum port to hook a guage to and probably pull the Kent cam out to install a stock one. I know it is something fundamental I'm missing but can't for the life of me figure it out. Keep the suggestions coming. I will follow each of them again, even if it for the 15th time. I wonder about the size of the exhaust, maybe it isn't scavenging the old gas enough? It is a big deal to experiment with that though. I am slow and will burn an entire saturday fabbing and fitting a pipe. Hopefully some wizard will tell me that size is fine...
JC
 
My high compression 1500 likes to idle rich and high. I can get a stable idle around 900 RPM and a mixture of 12:1 to 13:1. Anything less causes the same symptoms you speak of.
 
This sounds a lot like the problem I once had. The low-pressure fuel pump couldn't push fuel through the filter between the pump & carb. Got a big vapor bubble in the filter, which was easily visible since the filter had a clear plastic shell. In the end, I just used a filter ahead of the fuel pump (a Facet one) and figured that should do it.
 
Mine's doing the same thing at the moment. No idea why, but I'll be installing a low-pressure pump out back and ditching the FPR this weekend. Also planning on resetting the carb, going through the whole 'best lean' procedure again, and redoing the timing.

I'll let you know if it yields any results!
 
I pulled hair over this same issue (and at 47 I still have lots of hair and I don't really want to do anything that would cause unnecessary loss of it)- and I finally got tired of it. As great of a forum this is, the fact is that I'm the only guy I know that I can bounce off of- because I'm the only guy I know who has this vehicle around here. There's a guy down the street from me who works on stuff like Lotus 11's and he doesn't even want to look at a Weber. I can't see another one or get together with someone else. For me, I never had a baseline to begin with- I never owned one of these things (Weber's or MG's or worse- both) before and mine wasn't a running vehicle to begin with. I can only state from what I have learned..


1. It's loading up on fuel. Same problem I had. I've seen every excuse to compensate- timing, idle, etc. Every machine I built before didn't require ridiculous timing advance or high idle. Even my mild cammed 400 small block and my blower motor 5 liter Mustang didn't have these issues. That's a copout. I nearly went mad over this- I spent weekends over timing, idle and mixture and I could never get a baseline- time I could have been doing enjoying other things, such as driving this thing had it worked correctly.

2. On 1500's the poor sealing of the intake because of intake/exhaust manifold thicknesses will make it very difficult to get a good sealing on the intake to head, which will yield the symptoms of a leaning out engine that some feel a need to compensate for by richening the mixture, higher idle and overtiming. It's really important to make sure you have even torque on the intake/exhaust- I had to cut washers to make up for the difference in intake/exhaust manifold thickness, use a thick gasket ( the Pacesetter headers require a thick gasket and the company will sell the gasket direct over the phone) and I ended up using Permatex on the intake side to get a seal.

3. Before I ditched the Weber 32/36, I had to run a fuel pressure regulator and a gauge to see what I had- with a factory pump and then a Carter 4070 electric (which was very quiet as long as the thing is never fastened to anything made of steel). I also could have gone mad on jetting the thing- but why?

All I want is a car that I can drive and enjoy. I'm an IT guy. I work on networks all day long. That doesn't mean that I want to work on computers all day long- I just want them to carry out the task that they are used for. The point is I want a machine I can drive and enjoy and I could care less about what size jet is in the carb.

Now I just do it with a Holley 5220 (Weber clone) GM fuel system with half the crap, built in fuel filter, no regulator and the factory 1500 mechanical pump. Carbon copied the GM setup from the vehicle the carb was made for- and it didn't need a regulator or an electric fuel pump. Now I have zero hesitation when I put my foot on the accelerator pedal (and no matter how hard I may choose to do that), no fuel smell, no loading up at idle, easy adjustment and progressive secondaries- funny that I thought that when I bought the Weber I was going to get that. It's not no DCOE sidedraft eye candy, but nice musclecar feel when you stab the thing- and smooth 850rpm idle. I tried to make my engine compartment nice, but really- who see's it?
 
Thanks Duncan...let me know what you find out.

Gmichael - I agree that it is loading up on fuel. I'm pretty sure that is the case anyway. The only thing that makes me not want to replace the weber right away (besides the money) is that I had similar problems with Zenith Stromberg. I may try your thicker intake gasket trick first. I want to put a header flange on the collector anyway instead of the slip fit it has right now. What GM vehicle did you pattern your fuel system after? I can start shopping for best prices to see what I am up against. I'm way into my paint and body budget on this thing and haven't done a lot of body work yet...lol. And thanks for the advice.
Also, what did you do for an air filter?
JC
 
gmichael52 said:
Now I just do it with a Holley 5220 (Weber clone) GM fuel system with half the crap, built in fuel filter, no regulator and the factory 1500 mechanical pump.
Click to expand...

Is this the one?

https://tinyurl.com/5pujzp

what do you use for the intake manifold? the original or the webber?

do you have pictures?
 
I'm no fan of DGV's... but here's somethin' I'd do in the circumstance:

Get the engine up to temp by driving around. When the "problem" starts to manifest itself go to the driveway, idle for as long as it'll allow, switch off and (with an eye to safety here, please!) unbolt the carb and linkage... lift the thing and see if there's a puddle/pool of raw fuel in the bottom of that manifold. Looking for a dripping accel pump, needle/seat, etc. in that carb if there's gas in the manifold. Just an idea to rule out some of the "mystery".
 
Hey gmichael & JP,
That looks like something that might work for me.
I've got the old Hitachi downdraft carb on my Nissan 1500 and it runs "ok" but it would be nice to have something better.
I've been thinking about finding a rebuilt Hitachi, but maybe a Holly like that would be a step up. Something to think about.

JC - it seems you've got just about everything in there but the kitchen sink!
Hard to believe after all that it just wont run right.
Maybe its something simple? Have you looked at your plugs to see what color they are turning with all this? Are they all even, or are they lighter on 1&4 and darker on 2&3 etc...?
 
"""""is that I had similar problems with Zenith Stromberg. """"""""""""""

definitely move the electric pump to the back close and lo to the tank...altho thats not the real problem.

Get the car so as to have the problem at hand ...with the fuel pressure gage inline observe for change in pressure at that time.
Also first remove the carb top and look for crud in the bowl area. As this is ongoing with the old carb you might have a clogged screen in the tank, or crud from the tank moving downline. look for dribbling gas in venturis especially when you shut off the motor. inspect the needle/seat with a stronggggg lite for crud/pits/tears.

Plan b is to change the coil.

Plan C is a ruptured power valve in the carb.
 
Good suggestions everyone. There was a difference in the plug color at one time. A new dizzy from Jeff took care of that. It came with coil, cap, pertronix and the works. Now they are all nice and dull brown colored. There is a small amount of crud in one corner of the bowl of the carb. Not too bad but there is some. I have put a new tank and lines on the carb but the fuel pump was left from an older rusty tank. The weber was new and I utilized a new filter before and after the fuel pump. I don't think it is a delivery issue as I can run 90mph for about a mile and a half before the engine starts to starve for fuel. It never starved till I put the fuel regulator in the circuit. I will look for the puddle of fuel this weekend. I wonder what I will find? I've been suspecious of the power valve for a while now. Acutally considered pulling it out of the bowl and blocking it off to see if it made a difference.

I'm no fan of the weber either Doc, I was fed up with the Zenith and thought this might be the easy way out...you know how that goes.

And Zimmy, I followed your painting project very closely. I don't post much but read a lot. You did a nice job. When I paint mine, I'm stripping the tub and starting from scratch. I've got some metal to weld in as well. It will probably take me 12 to 18 months to complete at 3 or so hours every night.
JC
 
Carter 4070 pump going on today... I *will* get to the bottom of this.

I can't understand why the Holley, which is simply a licensed copy of the Weber after all, wouldn't have the same problems, if it really is a design flaw?
 
Carter's halfway on...JC, you making any progress?

Oh, my coil's also a little suspect, and I have a Fireball hi-spark coil to go along with the ignition management, so that'll be going on as well.

Weber was rebuilt last year, I really hope it's nothing internal.

I think I *may* have had a brilliant idea...

So I've cut the fuel lines back by the tank, to splice in the Carter pump. Now the stock fuel line, of course, runs over to the driver side, and exits near the mech. fuel pump.

BUT, the fuel return line runs along the passenger side and exits right up near the carb. :wink:

AH HAH! Says I... My fuel return / vent system being long since departed...

What do y'all think? Use the 'return' line as the new supply line? Same diameter, good routing, and it exits in just the right place to then run a short soft line to the carb.
 
I don't see why the return line won't work. Just make sure it is clear before you use it. Might flush it out a bit first before you hook it up. Hope it works out for you.
JC
 
Back
Top