Volvo won't crank

D

Douglas Pollard

.
Oct 30, 2019
64
Hi all, I have a bit of a problem. When I try to start my volvo engine
it will not crank beyond top dead center and may be firing backwards.
She seems to possibly fire before reaching the top of the stroke. This
would seem to be a timeing problem with the injector pump. After
reading through the manual it says to remove the cover to see the timing
marks and see if the marks line up when at top dead center. I am
working from memory here as I don't have the manual at this moment. In
any case it tells you to rotate the high pressure pump until the marks
line up. MY question is how do you rotate the pump when the fuel lines
coming off of it are steel tubing. That would seem to have to bend the
tubes. Has anyone done this? It would seem that the pump would have had
to rotate to get the timing off in the first place. That would appear
to mean that the mounting bolts of the pump might be loose? It would
seem with the pump being driven by a gear train, the pump rotating would
be the only way the timing could have changed unless a gear broke which
seems unlikely. I sort of got into it with a local diesel mechanic who
is telling me the engine needs to be replaced. I know better than that,
you just don't replace an engine because the timing is off. Of course
he wants to sell an engine. Anybody got any ideas?
Doug
 
T

tim_klynn

.
Feb 12, 2008
337
I don't know anything about volvo diesels (other than they are made in Sweden?), but on my navistar 7.3L (which is not in the Vega) I use a lever to turn the injection pump. Turning it so the base (~2.5" dia) rotates about 1/16" or so changes the timing a few degrees (the steel lines flex that much). Even if the pump affixing bolts worked a bit loose, the pump probably wouldn't be able to rotate that much before it met with resistance (fairly stiff steel lines). The 7.3l does have static timing marks to line up on the pump and housing (gets the timing set withing 4 degrees or so). The only way I could see timing getting that far off is if, like you suggest, some ip gear teeth got broken or stripped off, or there was some internal failure in the pump (I assume old volvos use mechanical pumps and not some kind of fancy computer controlled common rail injection system).

If the engine won't turn past tdc, maybe there is some type of fluid (diesel/water) in the combustion chamber that is incompressible.
If I were trying to figure it out (knowing nothing about volvos) I would try the cheap stuff first:

I would try pulling the injector(s) or glow plug(s) to see if it cranks freely. If it didn't crank easily, that would probably be bad news. While I had the injector/glowplug out I'd check compression. If there is a compression release, see if that is working and lets the engine crank over.

Next I would check to see if the injector had a good spray pattern or just squirted a big slug of raw diesel fuel. If the spray pattern looked good, and the compression was good, I would try to figure out if it was a timing issue. If the pattern looked bad, I would try a new injector or pump.
However, chances are good that someone that knows something about volvos will give you a better answer than this one. If you decide to replace your Volvo with a 7.3 Navistar, I can probably be more helpful....Good luck -Tim
 
G

groundhogyh

.
May 30, 2006
1,075
Isnt the bosch pump like a rectangle?
I recall the thing you turn for timing to have a round base.
Check the log history for more info.
Also, do you have the pdf engine manual?
rb
 
G

groundhogyh

.
May 30, 2006
1,075
.....and..... did it work before?....... and now the timing is way off?.......I would suspect something big has changed or broken or come loose............ the engine worked ok for many years and now its exploding before its timing spot?
rb
 
R

rogerefairest

.
Jul 6, 2007
106
You know, you leave to go somewhere on your little boat and end up somewhere
else, I should have learned that a long time ago.

So we took off from London to get to Darwin the Long way round, I should have
said, the long, long, long way round.

We are in Gibraltar now and staying put for a while here is not a bad spot, if
more interested read it in www.svoceansunrise.com

Cheers

Roger
 
G

groundhogyh

.
May 30, 2006
1,075
LOL.
Ive read articles that Gibralter is like a black hole.
Once you get in there and comfortable, its hard to leave.
WHen you do leave, they meet at the dock and throw you a party, then come back about 3-4 hours later to meet you back and have a welcoming party.
rb
 
T

trevy_kins

.
Oct 31, 2019
230
Doug, just wondering, have you checked to see if you problem has
something to do with the decompression lever itself?



From: AlbinVega@yahoogroups.com [mailto:AlbinVega@yahoogroups.com] On
Behalf Of Douglas Pollard
Sent: August 12, 2010 11:33 AM
To: AlbinVega@yahoogroups.com
Subject: [AlbinVega] Volvo won't crank





Hi all, I have a bit of a problem. When I try to start my volvo engine
it will not crank beyond top dead center and may be firing backwards.
She seems to possibly fire before reaching the top of the stroke. This
would seem to be a timeing problem with the injector pump. After
reading through the manual it says to remove the cover to see the timing

marks and see if the marks line up when at top dead center. I am
working from memory here as I don't have the manual at this moment. In
any case it tells you to rotate the high pressure pump until the marks
line up. MY question is how do you rotate the pump when the fuel lines
coming off of it are steel tubing. That would seem to have to bend the
tubes. Has anyone done this? It would seem that the pump would have had
to rotate to get the timing off in the first place. That would appear
to mean that the mounting bolts of the pump might be loose? It would
seem with the pump being driven by a gear train, the pump rotating would

be the only way the timing could have changed unless a gear broke which
seems unlikely. I sort of got into it with a local diesel mechanic who
is telling me the engine needs to be replaced. I know better than that,
you just don't replace an engine because the timing is off. Of course
he wants to sell an engine. Anybody got any ideas?
Doug
 
N

n3935j

.
Oct 31, 2019
58
low battery or poor starter circuit connections! You can check the timing
(pretty close) by hand cranking the engine ( with the decompression lever up)
and the injector line disconnected at the #1 injector. Turning the flywheel
slowly as you come up to top dead center on the compression stroke for the #1
cyl. you should see a squirt of diesel around 10 degrees before tdc. The
good news is it sounds like it has lots of compression. Your description
reminds me of trying to hand start my trusty Volvo by using my puny arms all by
myself!

________________________________
From: rchrdcoe coe.richard@...
To: AlbinVega@yahoogroups.com
Sent: Fri, August 13, 2010 9:40:05 AM
Subject: [AlbinVega] Re: Volvo won't crank


sounds like a low battery. are you shure the batterys are fully charged?
 
W

wemccourt

.
Jul 5, 2006
49
Doug,

Sounds like your start relay is stuck in the energized position. The start relay should only be energized, thus pulling in the solenoid coil and engaging the start gear to the flywheel to crank the engine over, when the key is advanced thru the ON position to the START position. When released back to the ON position, the start relay should be de-energized which should allow the solenoid to become de-energized and retract the start gear to dis-engage from the flywheel (there's a fairly robust spring to make this happen).

Works just like a car in this function.

Bill McCourt
Reston, VA
 
W

wemccourt

.
Jul 5, 2006
49
You're correct in your assumption. The Start Relay (the one that connects the starter to the battery-big cables) is controlled by a smaller relay which is directly connected to the key/start switch. When the key is released and it springs back to the Run position, the circuit that closed the large Start relay should open and release the start relay back to the de-energized state, removing the battery from the load of the starter motor. This will also prevent the start motor from overheating from the constantly energized state.

It sounds like someone has gotten into your starter control wiring and got things crossed up. I think there's a wiring diagram in the VEGA manual (should be in the files section of the group website) and you could do point to point wiring checks against the diagram.

Bill McCourt
 
W

wemccourt

.
Jul 5, 2006
49
Doug, I've just examined the wiring diagram for both the 022 gas engine and the MD6A and for the starting circuit they're nearly identical. The starting control relay and the large starter contactor are contained in one assembly. Both diagrams are located in the FILES section, the MD6A is the one called 26.GIF and the 022 gas engine one is in the VEGA Handbook.pdf file.

I would recommend that you do a hand over hand wiring check to make sure everything is connected where it belongs and that there are no "phantom" (undocumented) connections that may be inadvertantly holding your start circuit in the energized state by providing unintentional ground paths or voltage supplies where none should exist. Removing any extraneous wiring should correct any issues you may have with the engine control/starting circuit.

Sorry if I've muddied that water by shooting from the hip before looking at the wiring diagrams. (Ready, shoot, aim.)

You can also possibly redesign your starting circuit from generic 12 VDC diagrams you might find in the 12VDC doctor, This old Boat or similar books. Wiring in Motorhomes & RV's is very similar to a boat's so a circuit described there should work on a boat as well. They're all pretty much the same.

Bill McCourt
Reston, VA
 
You must log in or register to reply here.

Top Bottom