Put your "small" motor caps on ...

Mudrat

Well, I'm about confused on this one.

The engine:
4.2L, bored .030 over, cross drilled, ground and polished crank, stock cam, balanced rotating assy, minor smoothing on the ports (nothing radical), valve spring pressure was matched when the head was reworked by the race shop, stock intake, exhaust, Weber 38 DGES carb. New fuel pump, water pump, Alt, rebuilt P/S. Belts are fine (new) and tight, oil pres ₅₀# running about 20# at idle. Oh yeah, less than 1000 miles on the rebuild.

The problem:
I can get it to start and run, got the timing set fine (total of 24* at 1600 RPM), runs really well - then dies at speed. Starts right back up when cool, takes a couple tries when at temp, but starts and runs.
Daughter child (her YJ) has had it die several times to/from school (4 miles) and didn't even make it out of the driveway this AM (25 yards) 111!!!

What I've done (three times):
Double checked timing
Checked for Vac leaks with either
Readjusted the lean idle circuit on the Webber
Tried to rationalize the vac lines since I don't have all the smog crap the 'plumbing' ... um ... is .. ah ... different than the TSM.
Checked the timing again

Test drove it again tonight and it 'stumbled' a couple times slowing down for a stop lights/signs, but didn't die when stopped. Got back to the house and let it idle and it would randomly 'stumble' every 20-30 seconds. Exhaust smells a little rich but not terrible.
I put the timing light on it with the vac line still on the dizzy and the timing was jumping all over. That should tell me there is a vacuum leak somewhere but I'm not so sure any more Could I be pulling to much vacuum somewhere?

Anybody got any clues here????

Thanks
Pat

pyagid

i have to think about this one. I know i was having the same issue for a little while, I just need to remember what it was. What do you have for an ignition system on it? How long ago did it start doing it? Make sure there is no leaks around the weber, or adapters for it. Any valve noise? Vaccum advance working properly? If you hold vaccum to it with a hand pump? I will try and remember what my issue was -paul

Mudrat

pyagid wrote
i have to think about this one. I know i was having the same issue for a little while, I just need to remember what it was.

What do you have for an ignition system on it? How long ago did it start doing it? Make sure there is no leaks around the weber, or adapters for it. Any valve noise? Vaccum advance working properly? If you hold vaccum to it with a hand pump?

I will try and remember what my issue was

-paul

Thanks Paul - haven't put a vac guage or pump on there yet :-|
Right now it's the stock setup that the shop installed. I need to put the HEI back on anyway - and it's time to rip out all the "extra" wiring since the Carter's gone - don't need that stinking computer!! :t: Really wanted to make it run right before I installed any new problems, but oh well.... :razz:

shawn

What iginition? I would replace the coil and module. I know that coils stop working when they are old and they get too hot.

Blown7

shawn wrote
What iginition? I would replace the coil and module. I know that coils stop working when they are old and they get too hot.

I'm thinkin the same, or cap and rotor. Jeff

Mudrat

Hi guys - just got back from Fuzz's place in Lancaster. Drive back SUCKED!!! DC traffic is the worse in the world :razz: ~250 miles back took over 6hrs - but started driving from my buddies house west of DC this morning so add 3 hours to that today. Averaged 20mph coming around DC on 495 8) Then I get home and there's only 1 shot of Jack left #-o :smile: :smile: I'll unload the truck tomorrow and pop the TFI stuff back in. The current setup has the old coil, but new cap, rotor, wires and plugs. Plugs look good and I'm with y'all on going after electronics now. Can't seem to find a fuel or timing issue. Will let ya know what I find. Thanks :t:

youdidwhat

stumble at Temp :-| wonder, did you put new fuel filter in, are your hard fuel lines too close to the block (vapor lock) how long did it sit prior to your rebuild(build up in the fuel tank) how much pressure are you getting from your fuel pump. It's a carb, so O2 sensor should not be an issue. does it have a timing advance module in the dist.? I had one in a ford that when hot the darn thing would not run, ten min. later and she would start right up and act fine untill it got hot again. just so more ideas, some you may have covered, some not.

Mudrat

youdidwhat wrote
stumble at Temp :-|
(1) wonder, did you put new fuel filter in,
(2) are your hard fuel lines too close to the block (vapor lock)
(3) how long did it sit prior to your rebuild(build up in the fuel tank)
(4) how much pressure are you getting from your fuel pump.
(5) It's a carb, so O2 sensor should not be an issue.
(6) does it have a timing advance module in the dist.?
I had one in a ford that when hot the darn thing would not run, ten min. later and she would start right up and act fine untill it got hot again.

just so more ideas, some you may have covered, some not.

Lets see, before I tell you what I found today which only PARTIALLY cured the issue ...

New fuel filter YUP. The stock filter has 2 outlets - one to the carb, one back to the tank when the carb back-pressure is up. With the Webber the fuel return is off the float bowl.
Fuel line is close to the heater hose :-| Need to look at that again.
It was running and driven but not everyday, 2-3 times a week???
Fuel pump is new, but I haven't put a guage on it - don't have one #-o
The O2 has been off since the previous owner at least. It's part of the sensor setup that is all going away :t: :idea:
Stock dizzy, vac and mechanical adv.
Stock coil and new 7MM plug wires
New cap and rotor put in at the shop, they got it up and running for me to drive home (I was on travel for two weeks and had no time)

OK, what I found/did today - this'll kill ya :idea:

Popped the cap off and grabed the rotor to remove it so I could install the bigger Ford cap, and found the button on the end of the rotor - well that's the problem, THERE WAS NO BUTTON :shock: What was there was the black plastic and the metal strip from the center to the end, but the end piece was laying in the bottom of the dizzy!!! :shock:

So she got a new ACCEL performance coil, and the dizzy parts of the TFI upgrade, and 8mm wires from mine :roll:

Current status is the stumbling has reduced significantly, but still there. Retimed (8* and 22* total @1600RPM), opened the plugs from 35 to 37 for the extra zap from the new coil (- maybe I need more gap? 40? With the TFI it say's 45?) and screwed with the vac hoses again. It runs well (I can just about chirp the 33's on dry pavement, it's easy to spin'm in a corner :t: ) except for the occasional stumble and is difficult to start when at running temp. I drove around looking for Jeeps to wave at for 30-40 minutes with no problems other than the occasional stumble? And hte exhause smells better - not as rich :mrgreen:

youdidwhat

next time you pull the plugs go to a hotter plug. IE split fire, Plat tip etc. go ahead and run it at.040 gap and see if that helps. are all the plugs in good shape, (no cracks in the ceramic, etc) wodden clothes pins help with vapor lock or insalate the hard line. with the over flow return. make sure you do have a clear path back to the tank. you may try some sea foam in the gas to clean out the system. just some more ideas, sounds like you have it most of the way licked though :lo1l:

grignac48

I had the same problem on my 88YJ. Ended up being that when I put the Weber on and stripped the Emmisions garbage off the computer would go crazy when warmed up. The timing would move all over the place. I performed the Nutter bypass running the ignition module directly to the distributor and eliminating the CPU. No problems after that. It was alot better and the timming was rock solid. Good luck it took me a week to find mine.

Mudrat

grignac48 wrote
I had the same problem on my 88YJ. Ended up being that when I put the Weber on and stripped the Emmisions garbage off the computer would go crazy when warmed up. The timing would move all over the place. I performed the Nutter bypass running the ignition module directly to the distributor and eliminating the CPU. No problems after that. It was alot better and the timming was rock solid.

Good luck it took me a week to find mine.

Thanks Grignac - that's the goal to do away with the computer all together, but seeing that may be the problem, will do it sooner rather than wait till I get it running right.
After your Weber, what timing and jet size did you end up with?

youdidwhat wrote
just some more ideas,

I was thinking about just re-routing the fuel line - but I think your insulation idea will be a quicker - but short term - fix.

Reading the 411 on spark plugs to get an idea of temp range - found this:
"Do not make spark plug changes at the same time as another engine modification such as injection, carburetion or timing changes as in the event of poor results, it can lead to misleading and inaccurate conclusions (an exception would be when the alternate plugs came as part of a single precalibrated upgrade kit). When making spark plug heat range changes, it is better to err on the side of too cold a plug. The worst thing that can happen from too cold a plug is a fouled spark plug, too hot a spark plug can cause severe engine damage"

Thanks again y'all I appreciate the help. I gotta get this nuked out in the next couple days since I'm leaving for a week in the woods (hunting) on Fri. :lo1l:

fuzz401

me I would rather run a colder plug and foul it out then run a hotter plug and tost a piston

Mudrat

I agree. When I pulled up the Bosch page to see what heat range these plugs are - I didn't even find them listed? 111!!!

Bosch R6 491 is what's listed on the plug. Resister, size 6, is heat the 491? If so that's pretty cold already - infact maybe too cold? 500-800 is what's recomended, but like I said that plug isn't listed anywhere on the Bosch page so I don't know if 491 is the estimated temp :-|

youdidwhat

411 on spark plugs to get an idea of temp range - found this:
"Do not make spark plug changes at the same time as another engine modification such as injection, carburetion or timing changes as in the event of poor results, it can lead to misleading and inaccurate conclusions (an exception would be when the alternate plugs came as part of a single precalibrated upgrade kit). When making spark plug heat range changes, it is better to err on the side of too cold a plug. The worst thing that can happen from too cold a plug is a fouled spark plug, too hot a spark plug can cause severe engine damage"

thank you for the tip... it probally saved me a heap of heartach.

youdidwhat

:-| here is the page

http://www.boschusa.com/AutoParts/FAQs/SparkPlugs/

if you follow that link and scroll down the page ( about 2/3 the way down) it has a Q/A that says

"does a bosch part number have meaning to help determin the specifactions of the plug"

then it has a link.. that link is all the info you wanted, about the plug number :?

hope this helps... :mrgreen:

Mudrat

Thanks YDW, I looked at that and the R6 491 didn't match up to any of those codes 111!!! And JFI after 1000 mi, the plugs are looking "normal"

youdidwhat

cool good that the plugs look normal :t: here is a bosch contact # if your intrested. Bosch Customer Service: 888-715-3616 (Monday thru Friday 8:00 am to 5:00 pm CST; for U.S.) I think its toll free... not sure though.

grignac48

I ran the timming at 9. I was running a weber 32/36 and ended up ordering the next larger jet size. I always wondered if I shouldn't of ordered the Weber 38 instead. I set the carb with a vacuum guage and looked for 11 in. The vacuum line stuff was a anoying but I eventually figured out how to make it work with the carb and the 4wd actuator and light. I got great gas mileage went from 9mpg to 19mpg on the highway. :happy7:

Mudrat

grignac48 wrote
I ran the timming at 9. I was running a weber 32/36 and ended up ordering the next larger jet size. I always wondered if I shouldn't of ordered the Weber 38 instead. I set the carb with a vacuum guage and looked for 11 in. The vacuum line stuff was a anoying but I eventually figured out how to make it work with the carb and the 4wd actuator and light.

I got great gas mileage went from 9mpg to 19mpg on the highway. :happy7:

RGR - I'm at 8* now, have the full jet kit (came with mine??) I'm thinking of dropping a size to see how it works out first. I DO like your MPG though :t:
Where did you put your gauge? The line on the inside (under the choke - ported dizzy vac?) or the manifold side (front port)?

Got home too late to do anything tonight, sun was down and I've still got to get all my gear ready for 10 days in the woods :!:

grignac48

I ran the stock jet size and found that it was hard to get a smooth idle and did not accelerate smoothly when warm. I also ran out of adjustment on the mixture screw and could not set it up like the manual said. So I played with different vacuum settings (9-11) at the carb connection and eventually changed the jets to larger ones. That made idle alot smoother and I had mixture adjustment, when you stood on it I could bark the tires. Course they were near wore out. The engine was a rebuild and may have been bored out. So your results may vary. I still have the original jets. Found them the other day. The gas mileage was when I was driving alot of highway speeds and a bad Catyalytic converter. After I replaced the exhaust and converter the milage dropped to 17-18mpg on the highway. I shoulda left it off. You must set your timing first. then set the carb. Depending how bad your set up is you may have to go back and reconfirm timing and readjust the carb again. :homework: