| Author |
Message |
scrivyscriv
Samba Electrician
Joined: October 04, 2011
Posts: 2922
Location: Memphis
|
 Posted: Mon Jul 13, 2015 3:26 pm Post subject: Engine RPM drops at high speed & hot (SOLVED) |
 |
|
1971 bus with Rivy camper, 1641 engine with about 600 trouble free miles since rebuild, all stock cooling tin except bottom cyl tin (I know, I know). Running a cheater cam and Bugpack header/muffler.
009 distributor with 4-month old rotor, cap and wires, and an EMPI 34 pict carb.
Ambient temp today is around 93F - I made an interstate trip doing 60-65 for about 17 miles with no problem. The bus sat for an hour in the shade while we all ate, then I drove back to work on the interstate again. Made it about 5 miles down the road and then the engine started losing speed all of a sudden. My first thought was "fire" so I immediately pulled over and found nothing wrong, engine just purred like a cat. Fuel filter had a lot of fuel in it though.
Made it half a mile down the road, got up to about 55-60mph, and lost RPM and started surging again. Pulled over and found nothing wrong. The engine would rev up just fine on the side of the road.
I got off at an exit and drove 30-45mph the rest of the way with no problems - I know the engine got pretty warm, I got the oil light flicker at idle when I coasted up to a light, and it would go out when I blipped the pedal. I think I'm running Rotella or something similar, at least a 10- or 15w-40.
Any ideas yall? Vapor lock? Coil going out when it gets hot? Points dwell? I don't know what to really look for since it's intermittent. I might make this my excuse to swap in an H30/31 carb from Tim and get my 205T distributor overhauled...
_________________
Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help.
Last edited by scrivyscriv on Mon Jul 27, 2015 5:53 pm; edited 1 time in total |
|
| Back to top |
|
 |
busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51130
Location: Surrey B.C. Canada, but thinking of Ukraine
|
| Posted: Mon Jul 13, 2015 3:52 pm Post subject: |
|
|
Points closing up or fuel pump pushrod binding in the plastic block would be my first things to investigate.
_________________
Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
Слава Україні! |
|
| Back to top |
|
|
Tcash
Samba Member
Joined: July 20, 2011
Posts: 12844
Location: San Jose, California, USA
|
|
| Back to top |
|
|
scrivyscriv
Samba Electrician
Joined: October 04, 2011
Posts: 2922
Location: Memphis
|
| Posted: Mon Jul 13, 2015 4:56 pm Post subject: |
|
|
Well, apparently I've had my metal fuel line routed totally wrong this whole time, and had no idea which part of the pump stand was supposed to be sanded.
What. A. Doof.
_________________
Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help. |
|
| Back to top |
|
|
scrivyscriv
Samba Electrician
Joined: October 04, 2011
Posts: 2922
Location: Memphis
|
| Posted: Tue Jul 21, 2015 6:28 pm Post subject: |
|
|
I worked over my fuel pump pedestal, but the surging came back on the next trip.
The points had a fat weld spot and the gap looked like it either wasn't set right or had opened up a lot. I filed them with my ignition tool but that Bosch tungsten is tough!
It ran fine in the parking lot, guess I'll find out tomorrow on the way to work in the midday Southern heat...
_________________
Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help. |
|
| Back to top |
|
|
busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51130
Location: Surrey B.C. Canada, but thinking of Ukraine
|
| Posted: Tue Jul 21, 2015 7:08 pm Post subject: |
|
|
OK, so then how about vacuum leak opening up when hot?, valves tightening up?, resistor failing in the rotor or a plug wire end?
You did put clamps on those fuel lines after that pic, right?
_________________
Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
Слава Україні! |
|
| Back to top |
|
|
airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12721
Location: on a bike ride somewhere
|
| Posted: Tue Jul 21, 2015 7:21 pm Post subject: |
|
|
Is there any way you can rig and see a fuel pressure gauge when the surging happens? I know it's tough when it only does it at speed.
How new and shiny is your condenser? I had one go out that only showed symptoms when hot, though it also stuttered at hot idle.
Robbie
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
|
| Back to top |
|
|
aeromech
Samba Member
Joined: January 24, 2006
Posts: 16961
Location: San Diego, California
|
| Posted: Tue Jul 21, 2015 7:31 pm Post subject: |
|
|
Any kind of temp gauge? How hot is the dip stick?
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound |
|
| Back to top |
|
|
scrivyscriv
Samba Electrician
Joined: October 04, 2011
Posts: 2922
Location: Memphis
|
| Posted: Tue Jul 21, 2015 9:14 pm Post subject: |
|
|
Let me clarify...
Surging and rpm drop at approx 60-65mph, flat out, approx 95F ambient.
A) clearanced pump rod and pedestal, no fix, problem showed up again on next hot day drive.
B) found pitted points with excessive gap.. Filed and gapped points to .016". Idled fine, will drive it again in the heat tomorrow to see if it comes back.
The engine seems to be running pretty warm. I've got all my tins, flaps and thermostat but it just seems hot.. May be normal. I'm putting a CHT gauge on it as soon as I get the thermocouple.
Timing was set when I put on the ugly 009 but I'll check it again
_________________
Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help. |
|
| Back to top |
|
|
busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51130
Location: Surrey B.C. Canada, but thinking of Ukraine
|
| Posted: Tue Jul 21, 2015 9:27 pm Post subject: |
|
|
It'll be interesting to see what you discover.
_________________
Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
Слава Україні! |
|
| Back to top |
|
|
airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12721
Location: on a bike ride somewhere
|
| Posted: Tue Jul 21, 2015 9:47 pm Post subject: |
|
|
600 miles on the rebuild? It's still breaking in! I'm hitting 4,000 and temps are just now starting to simmer down.
Like sniffing with an O2 meter, (do you have access to one?) a CHT gauge will show a spike if the combustion mixture is leaning. After becoming too lean, the temps will then drop as the cylinder misfires. That is, of course, assuming you have a fuel issue.
I'm not sure a CHT gauge will show any changes with an ignition issue. That is, unless you have a dead short in your wiring. The DD gauges can flicker/power cylcle if you have a short somewhere. (A friend's leisure battery wiring shorted out on a windy road once, and he caught it with the DD showing sporadic readings. Otherwise he could have lost his bus!)
Robbie
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
|
| Back to top |
|
|
richparker
Samba Member
Joined: November 24, 2011
Posts: 6981
Location: Durango, CO
|
| Posted: Tue Jul 21, 2015 11:03 pm Post subject: Re: Engine RPM drops at high speed & hot |
|
|
| scrivyscriv wrote: |
1971 bus with Rivy camper, 1641 engine with about 600 trouble free miles since rebuild, all stock cooling tin except bottom cyl tin (I know, I know). Running a cheater cam and Bugpack header/muffler.
009 distributor with 4-month old rotor, cap and wires, and an EMPI 34 pict carb.
Ambient temp today is around 93F - I made an interstate trip doing 60-65 for about 17 miles with no problem. The bus sat for an hour in the shade while we all ate, then I drove back to work on the interstate again. Made it about 5 miles down the road and then the engine started losing speed all of a sudden. My first thought was "fire" so I immediately pulled over and found nothing wrong, engine just purred like a cat. Fuel filter had a lot of fuel in it though.
Made it half a mile down the road, got up to about 55-60mph, and lost RPM and started surging again. Pulled over and found nothing wrong. The engine would rev up just fine on the side of the road.
I got off at an exit and drove 30-45mph the rest of the way with no problems - I know the engine got pretty warm, I got the oil light flicker at idle when I coasted up to a light, and it would go out when I blipped the pedal. I think I'm running Rotella or something similar, at least a 10- or 15w-40.
Any ideas yall? Vapor lock? Coil going out when it gets hot? Points dwell? I don't know what to really look for since it's intermittent. I might make this my excuse to swap in an H30/31 carb from Tim and get my 205T distributor overhauled...
|
To much here, had to quote it all. So...you have a freshly rebuilt engine and your running 4k on the highway during the initial break in? Seems like you're getting on it a bit much in the early stages. How about stop and go traffic? How much are you reving it before shifts? The initial brake in is like breakfast, it's most important and you should be easy on it. You say you're at 600 miles did you have the 400 mile service done? During that first time heads become loose and the valves tighten. If you haven't done this you should do it asap. The next service will be 1000 miles later then every 3000.
Looks like you're running a full flow set up, so I doubt your running hot however new engines do run warm for awhile. I do question your oil choice but there's a another tread for that. But since your light is flickering I'd say you should switch to a thicker oil like 20/50. I know guys that run Rotella, it's their winter oil. You can buy a IR gun from HD for $30, I did and mine is spot on. Great thing to have if you dont have any gauges.
Above you state that you don't have the bottom tins on. But then here you say you have all the tins. Did you install them and how long did you wait until doing so? Please don't say 600 miles...
The engine seems to be running pretty warm. I've got all my tins, flaps and thermostat but it just seems hot.
So the fuel pump is good, now you should re-torque the heads, adjust valves, set points (pertronix is a great upgrade) time (009 static at 10*), inspect the rotor and wires, change the oil (I bet you have a lot of metal in there) and put clamps on your fuel lines. Then go for a nice easy ride, it is still breaking in and will be for the next several thousand miles. Im in a similar situation, my bus just went in for the 400 miles service. It should be done tomorrow. Best of luck.
_________________
__________
’71 Westy build
Adventure thread
’65 Deluxe Build
’63 Deluxe Build |
|
| Back to top |
|
|
old DKP driver
Samba Member
Joined: March 30, 2005
Posts: 4145
Location: Los Gatos,Ca.
|
| Posted: Tue Jul 21, 2015 11:45 pm Post subject: High temps |
|
|
This reminds me of having a customer from out of town having a newly
rebuild' wanting to drive 3000, miles with a fresh engine without the first
oil change & valve adjustment.
warranty is in JEOPERDY
When I was a tech and lived in southern California and did an overhaul
the customer had NO OPTION OTHER THAN TO go to an authorized Dealer no further than 600 miles or the Warranty would be VOID.
_________________
V.W.owner since 1967 |
|
| Back to top |
|
|
scrivyscriv
Samba Electrician
Joined: October 04, 2011
Posts: 2922
Location: Memphis
|
| Posted: Wed Jul 22, 2015 12:38 pm Post subject: follow up |
|
|
Thanks for all the pointers, suggestions, and ideas, y'all.
Yes, I did just put the lower cylinder tins on at the 600m oil change. I kept forgetting to do it prior.
The oil wasn't very metallic.. My first oil change after cam break in had a lot of glitter to it, this 2nd oil change looked pretty normal, if not thin.
Unfortunately the points ajustment and repair didn't fix the problem, I had the same issue again today.
Problem comes up almost exactly 3.5m after I get on the road. First mile is city driving, two stop lights, slight decline but mostly straightaway. Next 2.5 miles are interstate driving, flat out with moderate acceleration, getting up to 60mph, give or take a few MPH.
At 3.5m, I feel it surge, with the pedal about halfway down, or a bit more. The surging IMMEDIATELY stops when I let up off the gas a bit, and I can easily maintain 50-55mph with no surging.
In the parking lot today with the engine warmed up and at idle, I shot some temps with an IR gun.
Ambient temp approx 90F
Pavement temp approx 135F
Engine case temp, measured under gen stand and distributor, approx 170-180F
Exhaust, measured at collector flange, approx 350-380F, hard to tell for sure
Oil filter and hoses showed about 180F as well
I shot the fuel lines too... at the filter, engine bay left, I got about 110F, exiting the pump was about 140F, and at the carb barbed inlet, 120-130F.
There's a fair amount of condensation on the intake manifold, but the symptoms don't seem like carb ice. My intake preheat runners were measuring very hot at approx 350F.
Robbie, I don't have a meter. I'm going to get an exhaust gas analyser in the next few weeks to get my carb tuned up right, but nothing right now.
When I did the oil change last week, I did not adjust the valves or check timing and head torque; in hindsight I certainly should have. It will all be done ASAP. The engine is coming out to get an alternator, so all the tins will come off and I'll get a CHT sender under the #3 while I'm inspecting and torquing.
_________________
Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help. |
|
| Back to top |
|
|
Tcash
Samba Member
Joined: July 20, 2011
Posts: 12844
Location: San Jose, California, USA
|
| Posted: Wed Jul 22, 2015 12:50 pm Post subject: |
|
|
Make sure you have the correct fuel pump pushrod for that fuel pump.
Fuel Pumps
Good Luck
Tcash |
|
| Back to top |
|
|
SGKent 
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
|
| Posted: Wed Jul 22, 2015 1:15 pm Post subject: Re: follow up |
|
|
| scrivyscriv wrote: |
Thanks for all the pointers, suggestions, and ideas, y'all.
Yes, I did just put the lower cylinder tins on at the 600m oil change. I kept forgetting to do it prior.
The oil wasn't very metallic.. My first oil change after cam break in had a lot of glitter to it, this 2nd oil change looked pretty normal, if not thin.
Unfortunately the points ajustment and repair didn't fix the problem, I had the same issue again today.
Problem comes up almost exactly 3.5m after I get on the road. First mile is city driving, two stop lights, slight decline but mostly straightaway. Next 2.5 miles are interstate driving, flat out with moderate acceleration, getting up to 60mph, give or take a few MPH.
At 3.5m, I feel it surge, with the pedal about halfway down, or a bit more. The surging IMMEDIATELY stops when I let up off the gas a bit, and I can easily maintain 50-55mph with no surging.
In the parking lot today with the engine warmed up and at idle, I shot some temps with an IR gun.
Ambient temp approx 90F
Pavement temp approx 135F
Engine case temp, measured under gen stand and distributor, approx 170-180F
Exhaust, measured at collector flange, approx 350-380F, hard to tell for sure
Oil filter and hoses showed about 180F as well
I shot the fuel lines too... at the filter, engine bay left, I got about 110F, exiting the pump was about 140F, and at the carb barbed inlet, 120-130F.
There's a fair amount of condensation on the intake manifold, but the symptoms don't seem like carb ice. My intake preheat runners were measuring very hot at approx 350F.
Robbie, I don't have a meter. I'm going to get an exhaust gas analyser in the next few weeks to get my carb tuned up right, but nothing right now.
When I did the oil change last week, I did not adjust the valves or check timing and head torque; in hindsight I certainly should have. It will all be done ASAP. The engine is coming out to get an alternator, so all the tins will come off and I'll get a CHT sender under the #3 while I'm inspecting and torquing.
|
do you have a rev limiting rotor in the distributor? Using distributor lobe grease? Those points looks nasty dirty - maybe a bit sticky and floating at RPM? Also maybe it is the photo but does anyone see a rubbing block left on those points?
..........
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
|
| Back to top |
|
|
Randy in Maine
Samba Member
Joined: August 03, 2003
Posts: 34890
Location: The Beach
|
| Posted: Wed Jul 22, 2015 1:20 pm Post subject: |
|
|
| My guess would be that the rotor is shaving the cap from the inside. I would find a more appropriate distributor for your application if it were me. |
|
| Back to top |
|
|
scrivyscriv
Samba Electrician
Joined: October 04, 2011
Posts: 2922
Location: Memphis
|
| Posted: Wed Jul 22, 2015 1:26 pm Post subject: Re: follow up |
|
|
That's a 'before' photo of the distributor when I pulled it off to check points. I cleaned it with some LPS degreaser, filed the weld spot on the points, and put it back together with a tiny bit of wheel bearing grease (It's all I had at the time, I just saw the thread on distributor grease from NAPA so I'm getting it NOW).
The rubbing block is there, but hard to see in this photo. You can also barely see the welded tungsten tit sticking out on the stationary point, before cleaning and filing of course.
I'm fairly certain I have a cheap Duralast set of points in my spares box in the back... I may just put them in and test drive it again. I couldn't file the weld spot 100% flat so my points could easily be floating like you mention
| SGKent wrote: |
do you have a rev limiting rotor in the distributor? Using distributor lobe grease? Those points looks nasty dirty - maybe a bit sticky and floating at RPM? Also maybe it is the photo but does anyone see a rubbing block left on those points? |
_________________
Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help. |
|
| Back to top |
|
|
aeromech
Samba Member
Joined: January 24, 2006
Posts: 16961
Location: San Diego, California
|
| Posted: Wed Jul 22, 2015 1:26 pm Post subject: |
|
|
Randy's right. Look at all the crap inside that distributor. Even the points are covered with debris. Whatever the reason, I'd try a new distributor.
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound |
|
| Back to top |
|
|
Tom Powell
Samba Member
Joined: December 01, 2005
Posts: 4855
Location: Kaneohe
|
| Posted: Wed Jul 22, 2015 1:33 pm Post subject: Re: follow up |
|
|
| scrivyscriv wrote: |
... Problem comes up almost exactly 3.5m after I get on the road. First mile is city driving, two stop lights, slight decline but mostly straightaway. Next 2.5 miles are interstate driving, flat out with moderate acceleration, getting up to 60mph, give or take a few MPH.
At 3.5m, I feel it surge, with the pedal about halfway down, or a bit more. The surging IMMEDIATELY stops when I let up off the gas a bit, and I can easily maintain 50-55mph with no surging.
...
|
That sounds like a classic clogged fuel filter and the engingine running on the fuel in the carb bowl. Accelerates well with the bowl full. Limited MPH because of the limited fuel flow. Cruises well, but won't climb hills.
Are the points missing the tungsten on one side? A 205T works well with my '69 camper and I carry another plug and play 205T in my tools and parts box.
Aloha
tp |
|
| Back to top |
|
|
|
