Logo
FULL SITE MENU

FIXING Cranks starts dies variable valve timing

W

wharfcreek

Member
"Well, for all of you who thou

"Well, for all of you who thought I was nutz, I FOUND the problem. And....I WAS correct!! This engine DOES have variable valve timing!! Again, you say I'm nuts...but the fact is, that the cam belt was 'hopping' a tooth every revolution, causing the came to come in and out of 'time' based on the number of teeth in that belt...which is what, 150...give or take? So, evidently, there's a couple of teeth in the cam sprocket that are fouled or plugged, or something. I'm incline to guess, not having removed it yet...but I'm just guessing that the low point, where the cam sat over the winter...fouled with rust and debris. As the belt passed over this spot every revolution of the cam itself, it ended up one tooth off each revolution. So....eventually, after cranking enough, the thing would come back IN time...fire up and run...and then drop back out of time with NO compression!! A very ODD symptom indeed...but one that I thought the experts in the field might appreciate knowing. And, for someone with over 40 years of engine experience...it's a new one for me too. But, for those who thought I was wrong about my description of the symptom....I guess you can now understand the problem...and that my description was right on the money!! I guess a guy with my experience CAN hear compression!! TSD"
 
"Thomas, I don't think tha

"Thomas, I don't think that anybody thought you were nuts. The symptoms you are describing clearly pointed out at a problem with valve timing and the most common cause we have dealt with in this forum has been belts with broken teeth. The same symptoms can also happen due to a loose tensioner or something else like you suspect. The tooth or teeth always will jump at the lower sprocket, which is the one with smaller diameter and half the number of theeth than the other two. This is why the timing of the valves and ignition remained in tune, but not with the crankshaft, so the engine would fire-up occasionally for a short period of time!!! It would be interesing to know what you find out when you remove the timing belt.

To change the timing belt, remove the water tank and heat exchanger, the raw water pump and copper pipe to the heat exchanger, the belt cover, and the crankshaft pulley. You may want to get hold of a copy of the Seloc or Clymer manual so that you install the belt correctly and set the tensioner according to specifications.

Here is one instance where replacing the timing belt has been discussed before.

http://www.marineengine.com/discus/messages/12487/70562.shtml


You can further use the search function in the forum and look for posts with the words "timing", "marks", and "belt" on the Volvo Penta Gas Engines forum."
 
"Hello El,

Actually, I thin

"Hello El,

Actually, I think I mentioned to you that I'm in the automobile business. I'm in contact with auto mechanics at different dealerships almost every day....some of whom are truly experts in today's modern technology. I'd have to say that when I described this problem to them, they DID think I was being as intermittently crazy as the compression I was talking about. But, I now feel completly exonerated!! As I tried to get people to understand....I didn't need a compression guage to know I didn't have compression...or that I DID have compression when the engine started to run. The 'cyclical' nature of this problem was the real odd part of it to me. I've experienced belts with bad teeth...and while the do jump around, there's no predictability to it. In my description of this problem, you'll note that I mentioned an appx 10 second crank time with no compression....then compression beginning to build, then enough to start and rev up the engine...then a die out with, again, no compression. REPEATEDLY....this same cycle, over and over...to the point of battery failure. I think this part of it was the real clue. In doing the math...this 'problem' repeated it's cycle exactly 2 crankshaft rotations X # of teeth on the belt...what ever that is I'm not sure, but it's about 15 seconds of crank time on my boat. Anyway....I read someplace .... "It's not the fixin' that's the hard part...it's the figuring out What to Fix that's difficult!!". So, here I am a week into this...and now I've only got a few more hours of work to get this engine running smoothly...I HOPE!!(Murphy's law withstanding!) I will need some kind of information in order to get this belt installed and properly timed. I could probably figure out the crank/cam part myself, but there's a counter-shaft on this engine...and I'm not sure if it's just there to drive the distributor...or if it's weighted in such a way to counter-balance the 4-cylinder vibration....or what. So....I'll go lookin'. But if you've got a specific process you can email me....that would be helpful...including a few pics if you've got 'em. Tomorrow I'll go find a belt someplace. Hopefully my local Volvo dealer will stock one. I have a feeling I'm going to hear those hated words: "Sorry, we'll have to order it...be in in about a week!"..lol

Anyway....the front of the engine is apart and were it not for lack of a replacement belt...it would likely be running right now!! I appreciate the support...and kindly thank those who have contributed!! Kind Regards, TSD"
 
"Thomas, the belt you are look

"Thomas, the belt you are looking for is pretty common, as it fits all the OHC Volvo 4 cylinder engines from the 70s and 80s.

http://www.autopartswarehouse.com/search/?N=1733+11881+4294966689+9318

The tensioner is also common:

http://www.autopartswarehouse.com/search/?N=1733+11881+4294966689+5904


You may also consider replacing all the 3 timing gears: the sprocket in the crankshaft and the two wheels (camshaft and distributor). You can probably get them from an autowrecker for $50-$75 bucks for the set.

Installing the belt is not complicated: align the dot on the camshaft gear with the mark on the valve cover; then align the mark in the distributor gear with the pointer in the block; then the mark on the camshaft sprocket with the mark in the block. Before installing the belt, remove nut 14 and washer 13

http://www.volvopentastore.com/BELT_TRANSMISSION_AQ125A/dm/cart_id.657400424--ca tegory_id.333015--list_time.1208135677--session_id.423214972--store_id.366--view _id.325805

then compress the spring into the spring guide and keep it in place by inserting a punch or pin through the hole at the right end of the spring guide. Then slide in the timing belt (the marks in the timing belt should slide into the teeth marked on the gears). Once installed, remove the punch from the tensioner and reinstall the washer and nut.

If you want more detail, please get a copy of the Seloc manual, as you may likely need it in the future and it is a good investment to have it.

Also, this post will give you an idea of the physical location of the timing marks.

http://www.marineengine.com/discus/messages/12487/88126.shtml"
 
"El,

Thanks for that refere

"El,

Thanks for that reference. I'd figured out the deal with the punch/pin on the belt tensioner, but I wasn't sure about marks on those gears. In particular, the intermediate shaft or dist. drive shaft...what ever the Volvo people call it (counter shaft?). Actually, for what I've got invested in this whole project, and for my intended use of this boat....I think I'm going to cut a corner and re-use the current gears. I've got a feeling that it would take a blow-torch to get these old things off here anyway....to much saltwater spray around the Chesapeake. I spent 3 hours cleaning up the cam and countershaft sprockets....and have only the crank sprocket left. I'm going to try to locate a belt locally tomorrow...and if I'm lucky, I'll have the engine purring by tomorrow evening. I do plan to investigate further that pointless ignition module. I think that's one thing I WILL spend some money on! But, I've got rotten seats and floors to replace....old torn canvas, carpet, fittings...and more to worry about. When I'm done, I'll have a pretty reliable little toy boat. But...the work involved....whew!! Anyway, these last few references have been a BIG help. I'm confident I can find the marks now...and finish the job. I did note the one posting about the difference in the marks between the one on the crank gear, vs the cut in the pully for ignition timing. I'll be sure to watch that, and if I have to remove that front pully....I will. But, I understand that the one is for cam timing, and the other is for ignition timing...not to be confused!! Again....thanks!! I'll likly be back in a few days with final results!! With Appreciation, Tom D."
 
"Tom, just one note of warning

"Tom, just one note of warning: you think you may end with a nice boat, but if the timing gears are pitted and you don't replace them now, the new timing belt won't last and it will start jumping in no time; then you will likely become stranded in the middle of nowhere for the sake of not spending now a few extra bucks. The timing gears are normally not difficult to remove (maybe you have to zip-cut the one in the crankshaft, though), but you will be the best judge.

Good luck with your project."
 
"El,

First, thanks for that

"El,

First, thanks for that tid-bit of advice. And, for the most part, I think you're correct. The only thing that makes any real difference here is the fact that I'm not too concerned if this does happen. My home is 'on the water'....and I've got a lot of friends in the area with boats...so a tow back isn't really a problem. And, I don't plan to go too far anyway.....so...I figure I'll just give it a shot. Also...you should see this engine....it looks like it's been sitting on the shore of the Chesapeak exposed to the elements for over 20 years!! I really don't want to attempt removal of these gears for fear the shafts may fail!! Then....I'm really in for some serious repairs!! So....I'm going to just file the hell out of these sprockets....clean them up as best possible...and give 'em a shot!! I think I can salvage them 'as-is'....and that will expidite this whole process of splashing this boat!! Thanks for thinking of me though!! I do appreciate it!! Kindly, TSD"
 
Back
Top