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could my my "loppy" kind of rough idle cause lower water circulation for cooling?and thus cause the fuel to boil in the manifold? I was in a drive through and the car sputtered and died and will not re start. This has happened a couple times now- only at a idle in gear in traffic etc., I'll verify later today but I can almost guarantee ( from the past times) that the points will need to be adjusted or replaced and then the car will fire right up. Another query, I am getting ready to change out heater core, if that is plugged does that affect the cooling system at all? Any ideas or suggestions welcome- frustrating problem That I though I had taken care of with a flush and new cap and thermostat. A bit of background- I used some radiator stop leak to try to stop the core leak- does that stuff mess with a cooling system???
Thanks!!
350 bored stroked to about 400, custom cam from mark, aluminum top end. complete factory cooling system including the shroud, stock fan , stock NEW radiator. Holley 670 street avenger, mechanical fuel pump. The engine started sputtering and died at under 200, I am guessing it is an overheating problem but it does not blow steam or water out, the temp gauge creeps up and then it sputters. I have an old thread here from the first few times it happened. I thought I had it fixed by flushing, new thermo and fresh anti freeze at 50/50. Could the rough idle be an issue at all do you think? I know most will respond that at 200 it is not "overheating" but as mentioned I watched the gauge creep up and then the sputtering and dying. Could the extra little heat from idling rough be causing my points to distort or??? as mentioned I'll go home and mess with the points or change them out and it will fire right up, currently it will spin and try to start but no spark until I get at the points. Could the sputtering and dying be from fuel "boiling" inside the carb / manifold? Frustrating to not be able to trust the car......could too much stop leak cause a problem? I used about a jar last summer and then another 1/2 jar a month later......thoughts????? again, this exact thing has happened about 5 times now since last summer. First 2 seasons on the road and never happened, I have changed nothing except as mentioned.
Last edited by boese1978; April 22nd, 2019 at 06:00 AM.
Good question Joe, I'll have to confirm but I believe it was a 2 or 3, again though, everything was fine for 2 years.......nothing has changed except the thermo which I believe to be working by feeling the upper hose. Does the rough idle in gear slow down water flow a lot????
OK, now that I've re-read the whole thread, 200F is not overheating. With a proper 16 psi cooling system, the coolant won't boil until it hits 250F or so. 200-210 when stopped at idle is not excessive, so long as it stabilizes there and doesn't continue to climb. I suspect this is not a cooling problem. Do you have fuel pressure? When it stalls is it flooding or leaning out? How old is the fuel pump? Does the car have fuel return?
New coil and tried swapping in another ( new MSD) last time it happened to no avail.......as far as I know I have fuel pressure, there is an inline gauge bu the carb, obviously I can't see it when the car dies.Fuel pump is a couple years old provided by Mondello. No return line, to me it sounds like it is running out of gas and there is/was no flooded fuel smell. When I did get it pulled away from the drive through the fuel pump pressure read zero, which would be from me trying to start the car??? or should it read the 7-9psi while cranking too?.......the problem is so intermittent I can not duplicate it. My idea of running hot was just because I watched the gauge creep from 185 to 200 then the sputtering started and it quit. The car runs just perfect outside this issue.
Wondering still if the rough loppy idle would have anything to do with the coolant circulation?
If your cam has a tight LSA or a lot of duration causing a pretty heavy lope the engine could just be flooding from unburned fuel, you may have to speed up the idle or get a higher stall converter so the engine is not pulled down so low when sitting still in idle
But why would this issue appear after 2 years of no problems????
"If your cam has a tight LSA or a lot of duration causing a pretty heavy lope the engine could just be flooding from unburned fuel, you may have to speed up the idle or get a higher stall converter so the engine is not pulled down so low when sitting still in idle"
When it dies, pull the air cleaner off, operate the throttle while looking down into the carb and see if there are 2 solid streams of fuel spraying. If it does there is fuel in the carb. On to check for spark. When was the last time you tuned it? What do the plugs look like? These cars are not known to go years without maintenance.
<200 should not be an issue. Sounds as if you have a heat soak issue. Fuel has a low boiling point. Turning to vapor, why it doesn’t want to restart. If your cooling system and timing is checking good. I would try a thicker/better gasket under your carb or a small spacer .5-1”.
But why would this issue appear after 2 years of no problems????
"If your cam has a tight LSA or a lot of duration causing a pretty heavy lope the engine could just be flooding from unburned fuel, you may have to speed up the idle or get a higher stall converter so the engine is not pulled down so low when sitting still in idle"
Good question. Maybe the tune isn't what it used to be. As was already covered, 200* isn't hot. Do you have a wood or phenolic spacer under the carb? They really do help to prevent fuel boiling. Also, my little S10 truck with the 2.2 4 cyl runs terrible on the winter formula gas here, I can tell right away when the stations switch to the summer formula. I would also say a bad coil if you hadn't already replaced it. Are you sure there is no vacuum leak? Could be something leaking when it gets hot and expands. Could the vacuum line to the modulator be cracked under the car?
When it dies, pull the air cleaner off, operate the throttle while looking down into the carb and see if there are 2 solid streams of fuel spraying. If it does there is fuel in the carb. On to check for spark. When was the last time you tuned it? What do the plugs look like? These cars are not known to go years without maintenance.
I'll look for the streams of gas, Tuned last July with all new and then parked it to be started and run about every week during the winter. Plugs look normal and as stated the car simply runs perfect aside from this. Perhaps you can answer this- should there be fuel pressure registering on the in line gauge while cranking the engine? Got it home the other night and the gauge is at zero, Nothing shows while cranking it to see if it will pop off, stays at zero.........can a fuel pump going bad act like this? Ie: run perfect, go through what I am going through and then be fine again? ( please remmeber this issue has happened a half dozen times)
<200 should not be an issue. Sounds as if you have a heat soak issue. Fuel has a low boiling point. Turning to vapor, why it doesn’t want to restart. If your cooling system and timing is checking good. I would try a thicker/better gasket under your carb or a small spacer .5-1”.
I do have on the shelf a phenolic spacer, worth trying???? problem is I am not 100% of what the actual issue is.....
Good question. Maybe the tune isn't what it used to be. As was already covered, 200* isn't hot. Do you have a wood or phenolic spacer under the carb? They really do help to prevent fuel boiling. Also, my little S10 truck with the 2.2 4 cyl runs terrible on the winter formula gas here, I can tell right away when the stations switch to the summer formula. I would also say a bad coil if you hadn't already replaced it. Are you sure there is no vacuum leak? Could be something leaking when it gets hot and expands. Could the vacuum line to the modulator be cracked under the car?
99% positive there are no vacuum leaks, runs awesome and all lines are new,
update- had a few minutes after work, tried to start it, nothing. pour 1/8 cup gas down the carb and it pops right off ( that 1/8 cup burns off and car dies and will not restart w/o more gas), Where best to start trouble shooting the fuel system? any thoughts as to the correlation there appears to be considering the circumstances I have provided? Is a mechanical fuel pump either good or bad, or can they act up like this?
Last edited by boese1978; April 22nd, 2019 at 01:23 PM.
I'll look for the streams of gas, Tuned last July with all new and then parked it to be started and run about every week during the winter. Plugs look normal and as stated the car simply runs perfect aside from this. Perhaps you can answer this- should there be fuel pressure registering on the in line gauge while cranking the engine? Got it home the other night and the gauge is at zero, Nothing shows while cranking it to see if it will pop off, stays at zero.........can a fuel pump going bad act like this? Ie: run perfect, go through what I am going through and then be fine again? ( please remmeber this issue has happened a half dozen times)
Pull the fuel line at the carb, point it into some sort of qt container and see if there is fuel coming from the pump while cranking the engine. Usually takes 2 people. Uou may have low fuel pressure just cranking, normal is 6-7#'s running.
Pull the fuel line at the carb, point it into some sort of qt container and see if there is fuel coming from the pump while cranking the engine. Usually takes 2 people. Uou may have low fuel pressure just cranking, normal is 6-7#'s running.
will try that, as soon as i have a second set of hands
You may want to look at the inline fuel filter at the carb, I had one installed after my carb rebuild last year and it had a small spring loaded ball down the middle which closed off the fuel flow when the car wasn't running. Subsequently on a day a few months later my carb kept running dry before I could back it out of the garage. I checked for fuel flow from the pump, it was good, took out that filter and changed it with one without that stupid little ball and problem solved. Perhaps the ethanol in the gas makes that filter ball stick.
good luck...
I'm on board with fuel starvation and boil.
As mentioned verify the pump circuits squirt at least 3 solid pump shots when looking down the carb.
Make a temporary fuel line set up and "T" into the line between the pump and carb. Run a gauge with a long enough chunk of hose to your windshield secured with tape. Make sure its all good and secure. 5.5-6.5 PSI is good. Much lower or higher isn't.
Verify the rubber sections of the fuel line from the tank to the pump are not leaking. Suction leaks won't always show themselves as a PSI leak will.
A heat spacer under the carb will help. I never leave home without them.
Is the Holley an electric choke? Is it set properly?
Did you block off the heat riser crossover ports in the intake/heads? If not I highly recommend it, especially with an electric choke. That will solve 99.9% of carb heat soak problems. If you have the OEM exhaust manifolds remove the bi-metal stove flap and seal up the holes. The block offs can be welded into the intake in a manner in which it can be removed if needed. I did this to my iron intake. Carb heat soak solved. Even the divorced bi-metal choke has been modified. The only downside is it's somewhat cold-blooded but who drives these in the winter? Not I
Last edited by droldsmorland; April 22nd, 2019 at 07:59 PM.
I'm on board with fuel starvation and boil.
As mentioned verify the pump circuits squirt at least 3 solid pump shots when looking down the carb.
Make a temporary fuel line set up and "T" into the line between the pump and carb. Run a gauge with a long enough chunk of hose to your windshield secured with tape. Make sure its all good and secure. 5.5-6.5 PSI is good. Much lower or higher isn't.
Verify the rubber sections of the fuel line from the tank to the pump are not leaking. Suction leaks won't always show themselves as a PSI leak will.
A heat spacer under the carb will help. I never leave home without them.
Is the Holley an electric choke? Is it set properly?
Did you block off the heat riser crossover ports in the intake/heads? If not I highly recommend it, especially with an electric choke. That will solve 99.9% of carb heat soak problems. If you have the OEM exhaust manifolds remove the bi-metal stove flap and seal up the holes. The block offs can be welded into the intake in a manner in which it can be removed if needed. I did this to my iron intake. Carb heat soak solved. Even the divorced bi-metal choke has been modified. The only downside is it's somewhat cold-blooded but who drives these in the winter? Not I
I have an inline gauge for fuel pressure, when the car runs right I have about 6-7 psi, that is whatthe gauge read yesterday while and after cranking, it holds the pressure over night etc. Avenger 670 and choke works as it should, I have aluminum heads so no crossover as I recall. Using headers. Curious for someone to answer this question please- can a mechanical fuel pump work intermittently like this or is it either a good pump or bad pump?
Too hot at idle is now fuel related, need some help please
So, it now seems to be a fuel related issue as Joe surmised. I'm lost- see the thread below for background. As it reads " I poured some gas in the carb " yesterday and the car fired right up. Tried again later yesterday, no start as I did not pour any gas in, just "seeing what would happen". Get home from work today to start trouble shooting, turn the key and it fires up, choke is working , same awesome runner as 99% of the time. fuel pressure at a steady 7psi, responsive, tight throttle and so on. But I can not trust it......while visually inspecting I discovered that a stainless steel vacuum line was laying across the exposed + and - spades/ receptacles of the choke. I see no signs of arcing. But who knows while driving and vibrating.Could that be a part of what is going on? How best to proceed to try and isolate / replicate the problem? I'm all ears, well, eyes...... and thank you in advance. Taking it out for a short test ride now....... https://classicoldsmobile.com/forums...idle-gear.html
sorry for the new thread on the "same" subject please move if need be!
Last edited by boese1978; April 23rd, 2019 at 01:22 PM.
Yes Boese, shouldn't have started another thread. It makes us and you chase your tail. It makes the search feature numb(er) than it already is...harder to the search on specifics. Always finish out the thread. Ill let moderators decide if they want to move it. (Never mind tx Eric).
When it stalls out..... "As mentioned verify the pump circuits squirt at least 3 solid pump shots when looking down the carb". Didja do this?
The fact that you have a gauge present will make rigging up a remote gage tapped to your windshield all the easier. A mechanical diaphragm fuel pump typically will simply fail. You would not see 6-7 PSI Even though you have 6-7 PSI that doesn't mean it's getting into the float bowl.
Toss the Morain sintered brass type integral(carb mounted) filter the web page says it comes with, in favor of a paper element, the short GM paper filter, (it should fit, see pic). Pull the rubber valve out of it before installation. The Morain style filter could be plugged up but letting just enough fuel by to start, idle and run until a greater demand it summoned. They are well known for this.
Yes Boese, shouldn't have started another thread. It makes us and you chase your tail. It makes the search feature numb(er) than it already is...harder to the search on specifics. Always finish out the thread. Ill let moderators decide if they want to move it. (Never mind tx Eric).
When it stalls out..... "As mentioned verify the pump circuits squirt at least 3 solid pump shots when looking down the carb". Didja do this?
The fact that you have a gauge present will make rigging up a remote gage tapped to your windshield all the easier. A mechanical diaphragm fuel pump typically will simply fail. You would not see 6-7 PSI Even though you have 6-7 PSI that doesn't mean it's getting into the float bowl.
Toss the Morain sintered brass type integral(carb mounted) filter the web page says it comes with, in favor of a paper element, the short GM paper filter, (it should fit, see pic). Pull the rubber valve out of it before installation. The Morain style filter could be plugged up but letting just enough fuel by to start, idle and run until a greater demand it summoned. They are well known for this.
Thx for the feedback. When the car runs and starts it obviously does have the squirts, when it won't start no squirts. Strange how it just "happens"...you mention a "greater demand" this issue has happened in total about 6 times now over the past year and ALWAYS at a idle, in gear in a drive through or stop and go traffic or slow cruise through a car show, so very little demand. Why would the filter be plugged sometimes and not another though? I will replace the filters just because. . You guys also said I should trouble shoot when the problem arises again, how so???? I do have a spare , new fuel pump, worth swapping in or maybe next time I get stranded swap it in and see???Also, are you suggesting dr, to have a fuel pressure gauge I can see while driving to monitor it or what? Could this be a carb problem? suggestions and ideas are welcome! The car always has spark when this happens, just no fuel. I have a spark testor fyi and as mentioned when this happens a 1/8 cup shot of gas dumped in the carb and it will fire up.
Last edited by boese1978; April 24th, 2019 at 04:18 AM.
First, verify the fuel flow is filling the bowls as it should. If the PSI checks look up the line from the pump and gauge which is the filters. Step 2 is pulling the bowls and look at floats and needles & seats. Check float level and drop adjustments. (Watch video).
"Also, are you suggesting to have a fuel pressure gauge I can see while driving to monitor it or what?" YES...."Could this be a carb problem?" YES.
Do the above before crawling down the rabbit hole.
See the PDF instruction sheet as well as the tune video. These carbs are fairly simple to work on. Leverage other resources such as Holleys tech line.
So after a 2 hour drive yesterday, everything worked fine. The PSI stays steady through out the rpm range. Is it worth checking the floats etc when the car is running so nicely? or do I just need to wait for the issue to pop up again and then troubleshoot, kinda sucks.....
Ya agreed not fun not trusting your ride. Whatever it is it's likely it didn't self heal.
If it was me I'd pull the carb down for a look but I can do carbs in my sleep and I'm not ever satisfied until I solve the problem(I'm sure you can relate).
Check that inlet filter at minimum. That's basic quick n easy.
What Id suggest is make a list of troubleshooting steps from this email chain 1-10, most important to least.
Have some spare parts on hand, Fender covers, RTV, rags, hand cleaner, coveralls etc...the usual roadside bag of tricks. Put all of this and a well-equipped road box in the trunk with a makeshift creeper and drive it. If it occurs out on the road you'll be prepared with hopefully the right info and tools to find it and get it home. All this will at least make you feel better.
I run with one of those modern manual type bottle jacks with a folding crank handle too. Never use a bumper jack for safety and cosmetics on the bumpers.
.
Make sure you have FLATBED towing service on your insurance or AAA policies. Don't want anyone hooking an old school wrecker to a 68-69 bumper. (any bumper for that matter).
April 22nd, 2019, 04:12 AM
