DAMMIT RAY ! (old indian saying)

-
famous bob

famous bob

mopar misfit
Joined
Aug 14, 2011
Messages
20,633
Reaction score
9,685
Location
okla
It was about 80 degrees yesterday, got the 505" fish out for a little drive, seemed to be running better than ever,(close to being broke in). I had just put a 1 step hotter set of plugsin it. Got back after a short trip, shut it off to unlock the garage,
When I started it , it backfired thru the throttle body, w/ a couple of little poop noises in the mufflers. It ran a couple of hundred rpms faster than normal, which is 1150 idle. first thing I thot of was dropped valve, locked timing jumped, but all seemed to be well, I can see thru my glass valley pan. seemed to be running ok, just faster. Next , I thot maybe a ruined part in the throttle body, then maybe plugged fuel filters, or gas level too low and the pick ups uncovered, the fuel gauge was showing about 39 lbs, instead of 43. Two stroke motors will speed up a bit when running out of gas, but never had a car engine do it. Any guesses what happened ????? I`m going to start looking in to it today I guess.-------------DAMMIT RAY!!
 
Last edited:
Well,two stroke motors ,which I know a lot about,run faster as they run out of gas because the mixture leans out as the float level drops in the bowl.Been riding my strokes for 53 years and know that feeling well. So,if you apply that to a 4 stroke it could be an air leak . The pop sounds like an air leak
 
It's sucking air thru that gap.On my BMW K100 motorcycle the fuel injection has a throttle stop switch and it is adjustable.When it's not adjusted right the engine will pop and buck some from too much air as I back off on the gas or try to hold a steady throttle opening at a low speed like 30 mph.Really sounds like an air leak what you describe .
 
valiantwagonguy said:
It's sucking air thru that gap.On my BMW K100 motorcycle the fuel injection has a throttle stop switch and it is adjustable.When it's not adjusted right the engine will pop and buck some from too much air as I back off on the gas or try to hold a steady throttle opening at a low speed like 30 mph.Really sounds like an air leak what you describe .
Click to expand...
need to figure out why it backfired in the first place !
 
famous bob said:
need to figure out why it backfired in the first place !
Click to expand...
I had that happen to my TBI, turned out to be a cracked base gasket under the TBI unit created an air leak and rpm went up a couple hundred and stayed there. Check base gasket mine was in 2 pieces .
 
sabre67 said:
I had that happen to my TBI, turned out to be a cracked base gasket under the TBI unit created an air leak and rpm went up a couple hundred and stayed there. Check base gasket mine was in 2 pieces .
Click to expand...
been wondering about an air leak. too cold for me out right now tho. thanks for the input !
 
sabre67 said:
Let us know what you find :popcorn:
Click to expand...
Its turned cold again, and pouring rain, and I haven`t got back to it. After thinking about it, when I put it in park I might not have had it in fully, cause after the backfire, the motor wouldn't turn over, nothing. I sat there a second and pulled it in neutral,and it started and ran about 300 rpm too fast and wouldn`t idle down, everything other that that seemed to be ok. Thinking maybe a glitch in the n starter switch . ????? Hope it didn`t bend the throttle blades or something like that, "or worse !" I dropped a valve in one of my hemi`s back in the day, it acted the same way, but didn`t run as smooth. Fingers crossed !
 
Higher idle does sound like it’s a bit leaner.

But. On our E body, it started to do that. I went through same things.

Then I figured it out - the throttle linkage was ever so slightly binding in the casing. Just a very small difference in a small bend in the routing because of the intake differentiation. I put a heavier spring on it and solved the issue. Just an idea.
 
Deucemopar said:
Higher idle does sound like it’s a bit leaner.

But. On our E body, it started to do that. I went through same things.

Then I figured it out - the throttle linkage was ever so slightly binding in the casing. Just a very small difference in a small bend in the routing because of the intake differentiation. I put a heavier spring on it and solved the issue. Just an idea.
Click to expand...
thanks, but no binding !
 
A lot of times an intake backfire blows off vacuum lines that may be plugged into the intake. It could also blow the gasket out from under the TB as well. Any of those would result in a higher idle as they would be a manifold vacuum leak.

Isn't that thing pretty high compression? You need a colder than normal plug in that instance, not hotter.
 
RustyRatRod said:
A lot of times an intake backfire blows off vacuum lines that may be plugged into the intake. It could also blow the gasket out from under the TB as well. Any of those would result in a higher idle as they would be a manifold vacuum leak.

Isn't that thing pretty high compression? You need a colder than normal plug in that instance, not hotter.
Click to expand...
RRRRRRRRustyR R , hit it right on the head! I went out in the garage for a bit today, took the hood off and started looking for a reason for a vacuum leak. when it backfired it blew a rubber cap off the extra 3/8" vacuum port behind the throttle body, there are two 3/8" , the other is hooked up to my pvc valve. I couldn`t find the plug so I made one w/ a teather on it to contain it in case it happens again. Kinda like an explosion panel . Thank GOD it wasn`t serious ! ROB, I`ts only 10.3 comp. It has been blackening the plugs, even tho I have it set leaner than the built in settings. Easy to change stuff w/ the handheld for the fuel inj. ! HAPPY CAMPER AGAIN !!
 
famous bob said:
RRRRRRRRustyR R , hit it right on the head! I went out in the garage for a bit today, took the hood off and started looking for a reason for a vacuum leak. when it backfired it blew a rubber cap off the extra 3/8" vacuum port behind the throttle body, there are two 3/8" , the other is hooked up to my pvc valve. I couldn`t find the plug so I made one w/ a teather on it to contain it in case it happens again. Kinda like an explosion panel . Thank GOD it wasn`t serious ! ROB, I`ts only 10.3 comp. It has been blackening the plugs, even tho I have it set leaner than the built in settings. Easy to change stuff w/ the handheld for the fuel inj. ! HAPPY CAMPER AGAIN !!
Click to expand...

Black plugs could indicate low initial timing. Where do you have it set? Isn't it locked out? I caint remember.
 
RustyRatRod said:
Black plugs could indicate low initial timing. Where do you have it set? Isn't it locked out? I caint remember.
Click to expand...
Yeah it`s a locked dist., but the timing is controlled by the fuel inj. set up. It`s at 21 initial. Had it at 22 and it didn`t want to start when summertime hot. It was totally new and didn`t have much run time on it then tho. I have been thinking on bumping it a little more now that its got about 450-500 miles on it . I don`t get around to messing w/ it a whole lot, especially w/ the weather this winter. --thanks for the reply-
 
I'm old school with cars and motorcycles . Most of my bikes and all of my cars are mid 60's to early 70's two strokes and a couple 4 strokes. They all have carbs . Then I got this non running 1988 BMW K 100 . I had to learn all about EFI. This bike is the same as automotive. It's basically a 4 cylinder car motor laid on it's side and stuffed into a bike. What I learned working on this fuel injected liquid cooled 4 cylinder BMW motorcycle is that the slightest thing can cause problems like you are describing and the first place to look is at all the electrical connections.The whole system is run from the fuel injector computer and the mass air flow sensor and the temp sensor in the cooling system.There are so many things giving that computer input and all it takes is one loose wire,or corroded connection and you get a backfire or it runs rough ,or it won't run at all, Check all the plug in connectors and use dielectric grease on them as a starting point .Then if it still has issues look for air leaks. My money is on an electrical problem causing the initial problem of the backfire and now an air leak as a result of the backfire.
 
valiantwagonguy said:
I'm old school with cars and motorcycles . Most of my bikes and all of my cars are mid 60's to early 70's two strokes and a couple 4 strokes. They all have carbs . Then I got this non running 1988 BMW K 100 . I had to learn all about EFI. This bike is the same as automotive. It's basically a 4 cylinder car motor laid on it's side and stuffed into a bike. What I learned working on this fuel injected liquid cooled 4 cylinder BMW motorcycle is that the slightest thing can cause problems like you are describing and the first place to look is at all the electrical connections.The whole system is run from the fuel injector computer and the mass air flow sensor and the temp sensor in the cooling system.There are so many things giving that computer input and all it takes is one loose wire,or corroded connection and you get a backfire or it runs rough ,or it won't run at all, Check all the plug in connectors and use dielectric grease on them as a starting point .Then if it still has issues look for air leaks. My money is on an electrical problem causing the initial problem of the backfire and now an air leak as a result of the backfire.
Click to expand...
You musta missed what I found. Blew a rubber plug/cap off the extra vacuum port on the throttle body. Had another, and made a tether for it to retain it if it would happen again.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Can u say , "burst panel ?"
I think it was a neutral starter switch glitch that caused it to start with, because it would start in neutral and not in park. -------HAPPY CAMPER AGAIN ! LOL
 
See
famous bob said:
You musta missed what I found. Blew a rubber plug/cap off the extra vacuum port on the throttle body. Had another, and made a tether for it to retain it if it would happen again.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Can u say , "burst panel ?"
I think it was a neutral starter switch glitch that caused it to start with, because it would start in neutral and not in park. -------HAPPY CAMPER AGAIN ! LOL
Click to expand...
See, an electrical problem( starter switch) causing a plug to blow off a vacuum port
 
valiantwagonguy said:
See

See, an electrical problem( starter switch) causing a plug to blow off a vacuum port
Click to expand...
more like my dumbass didn`t have it in park all the way, made contact for a second, then quit. Will investigate further_____________
 
You must log in or register to reply here.
-

Back
Top