Tips, notes and suggestions (with a graphic illustration!) on changing the timing belt on a Volvo 740. Good stuff by longtime MVS Forum members.
dunamis » 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.
Retired MVS Contributor » 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 » 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 » 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…
Last Updated on August 19, 2020
