Timing belt Volvo 740 200k miles.

dunamis · Post by **dunamis** » 19 Dec 2010, 15:00

Hey All,

I replaced timing belt on above mentioned vehicle. Belt is properly alinged and checked it a few times by cranking car over a few times. Unfortunately though, vehicle will not start but only cranks over. Any advice is most welcomed. Thanks.

randyman · Post by **randyman** » 19 Dec 2010, 15:17

did it run PROPERLY prior to the belt change? Did the privious belt break or slip?

dunamis · Post by **dunamis** » 19 Dec 2010, 22:56

The belt did not break or slip. It ran 'ify' before the belt change. Piston 1 was misfiring at 1.5k - 2.0k rpm. Then it would work properly at higher rpms. The vehicle would turn off at various intervals while idling. We decided to start by 'reseting' the timing and install another belt. This is where we are at. Thanks for your help thus far.

Retired MVS Contributor · Post by **Retired MVS Contributor** » 20 Dec 2010, 06:32

This engine is non-interference and a broken timing belt will do no damage...The distributor is at the back of the engine and is driven by the camshaft so timing of the secondary shaft on the left side is not important, it drives the oil pump only...Since you are certain that the timing is correct I think you can assume that the timing belt is not your problem now...

Have you checked OBD for codes at the diagnostic socket on the left strut brace near the firewall?...

I would suspect the MAF since you were having idling problems before you changed the belt...The MAF is located in the big black tube on the left side near the alternator...If you have the Bendix system (most likely in the US) the MAF connector is on the inboard side of the tube facing towards the alternator...If you have the Bosch system, it is in the same place but faces outboard towards the power steering reservoir...

Disconnect the MAF and try to start the engine...Disconnecting it puts the system in "limp home" mode and will allow the engine to start and run with reduced efficiency and power...If it does start, you need a new MAF...

Kmaniac in California USA · Post by **Kmaniac in California USA** » 20 Dec 2010, 11:31

Before you go any further with this, please answer my question.

How did you index the crankshaft prior to timing belt installation?

I agree with Jerry that auxiliary shaft timing is not critical with the camshaft driven distributor. The camshaft sprocket timing marks are clear and difficult to miss. But alignment of the crankshaft can be confusing is not understood. How you answer my question will give me your thought process and possibly identify another hidden issue. I will explain further once I see your answer.

Retired MVS Contributor · Post by **Retired MVS Contributor** » 20 Dec 2010, 13:38

This indexing issue has come up before...In order to remove the belt, you need to remove the lower timing belt cover and the pulley/harmonic balancer...Once that cover and the pulley are removed, the IGNITION timing indexes are removed and should not be referred to when timing the belt...The timing mark for the belt is referenced between a mark on the front of the crankcase and a mark on the sprocket...

To remove that lower timing belt cover one needs to remove the pulley/harmonic balancer and the IGNITION timing marks on both the lower cover and the pulley/harmonic balancer are not even in the picture anymore...I cannot IMAGINE how one could confuse the mark on the crankcase with the mark on the now missing cover when putting the belt on, but apparently it has been happening because this is not the first time it has come up...

The issue is that the harmonic balancer is mounted in rubber which can de-laminate, slip, and move the IGNITON timing mark off far enough so as to be useless...But that is ignition timing, not belt timing...I doubt that this is the issue here...dunamis sounds like he knows what he is doing to me...

Jerry

dunamis · Post by **dunamis** » 20 Dec 2010, 20:48

Thanks to the both of you thus far. It may sound like I know what I am doing but i highly doubt it.

kmaniac - I'm not really sure what you mean by "How did you index the crankshaft prior to timing belt installation?" I looked up the diagram and instructions for the timing on this vehicle and 'it' seemed pretty straight forward with the marks and all. If you think i missed something maybe you can advise.

jerrymcc - i disconnected the MAF and it was a no go. can you point me to instructions for use of the OBD diagnostic tool?

Also, as an fyi i disconnected a spark plug wire and noticed that there is no spark when cranking the vehicle.

Kmaniac in California USA · Post by **Kmaniac in California USA** » 20 Dec 2010, 21:35

dunamis wrote:kmaniac - I'm not really sure what you mean by "How did you index the crankshaft prior to timing belt installation?" I looked up the diagram and instructions for the timing on this vehicle and 'it' seemed pretty straight forward with the marks and all. If you think i missed something maybe you can advise.

I'm not sure what your crankshaft timing marks look like inside your timing case, but I got real confused when I went to replace the timing belt in my '86 B230F. My Haynes manual said to align the "marks on the crankshaft sprocket guide plate and the rib on the oil seal housing". Once I got my timing cover off, I couldn't find these so called marks as they weren't intuitively obvious to me. Knowing that the crankshaft had to be at TDC, I assumed I could find this by just quickly reinstalling the lower timing cover and crank pulley and aligning the ignition timing mark to the timing scale on the case. Should work in theory, right?....In theory, yes, but in practice and in my case, WRONG!!! This reason this didn't work for me was because my ignition timing mark had slipped counterclockwise on my crank pulley by 46 degrees due to failure of the harmonic balancer. After removing and reinstalling the timing belt three times with no success, it finally dawned on me that maybe there was a problem with my original crank pulley, which I confirmed with I conpared it physically with a new one. Then I finally figured out the marks that required alignment for the crankshaft pulley. New crank pulley and proper alignment later, my Volvo has never run better.

I have been working on cars for over 30 years as a hobby and have installed many a timing chain and belt set on other cars with success, but mine was the only Volvo I have ever worked on and I made the wrong assumption when faced with a confusing situation. And I can understand how someone else with my experience might do the same thing as I with similar results. I just want to make sure that someone else didn't make the same mistakes I did.

Below is a picture of the timing mark illustration from my Haynes manual. It shows how the slot in the crank should align with a rib on the timing cover seal at approximately 11:00. If you verified the alignment of these internal marks for your crankshaft inside your engine, then your problem may not be related to the new timing belt installation. But if you somehow used the ignition timing mark on the pulley to set the position of the crankshaft, like I did at first, your timing belt is installed incorrectly and you may have a bad vibration damper and pulley as well.

Good luck and let us know what you find.

Retired MVS Contributor · Post by **Retired MVS Contributor** » 21 Dec 2010, 06:29

Kmaniac:

Don't feel bad, it is not the first time this happend...The confusion comes in because folks look for the mark on the crankcase at TDC when it is off to the left of center...Using the ignition index on the cover puts valve timing 30 degrees late...

Dunamis:

There could be any number of things wrong and you need to look at the OBD...The OBD unit is located on the left spring tower brace near the firewall...It has a snap-on cover that you remove to make the readings...The procedure and codes are pinned at the top of this forum, or, if you have Windows office in your computer, the two attachments I am posting should work for you...

dunamis · Post by **dunamis** » 22 Dec 2010, 14:51

again thanks to the both of you.

jerrymcc,

I ran the fault codes on the light diode and got the following code for fuel injection troubleshooting: 1-1-1, which accordng to the chart means fuel injection system is OK. the code for the ignition system troubleshooting i got was: 2-1-4, i looked it up on the chart and it says that the 'Crankshaft position/speed sensor faulty'.

Questions: 1) where is the sensor located, if you can point me to it i would greatly appreciate it. 2) i heard that the sensor when installed needs to be 'programed to the computer' for it to work properly. Can you verify this? if so how? thanks.