Engine doesn't want to start after being put back in car
Discussion
Quick run down of what I've done - taken the engine out to change the cams, spent two days timing the cams back in so I would really hope they are correct. Changed most of the fuel lines. Changed the front pulley and crankshaft oil seal. Engine was running generally OK before it came out (nearly 2 years ago!).
Engine turns over quickly enough, then when it gets close to starting it stutters/stalls/almost stops and sometimes wants to backfire. I know this pretty much means it is ignition or cam timing. Just want someone to check over the diag screenshots just in case I've missed something obvious. Adaptives have been reset. The trace is of 10 seconds of me trying to start the engine, you can see at 3 seconds I press the pedal slightly to give it a little bit of fuel.
Also I should add that the exhausts aren't currently connected.
Engine turns over quickly enough, then when it gets close to starting it stutters/stalls/almost stops and sometimes wants to backfire. I know this pretty much means it is ignition or cam timing. Just want someone to check over the diag screenshots just in case I've missed something obvious. Adaptives have been reset. The trace is of 10 seconds of me trying to start the engine, you can see at 3 seconds I press the pedal slightly to give it a little bit of fuel.
Also I should add that the exhausts aren't currently connected.
Did you change the 2 fuel lines that come out of the fire wall, under the water header tank ?
If you did, check you hav nt got them on the wrong way round.
apart from that i can t see why it wont start.
are you sure youve checked your cam timing right ? when your front piston is at TDC on either bank, the valves should be on over lap on the back piston on the same bank. ( i hope that makes sence )
If you did, check you hav nt got them on the wrong way round.
apart from that i can t see why it wont start.
are you sure youve checked your cam timing right ? when your front piston is at TDC on either bank, the valves should be on over lap on the back piston on the same bank. ( i hope that makes sence )
If it's back firing you've either got the leads wrong or the cam timing is out I'm afraid.
Check for Spark
Check for fuel
(guessing you've got them as it is attempting to fire)
Pull cam covers and check overlap positions for each cams in relation to each front cylinder TDC
Afraid it's now a case of double and re-checking everything you've done so far.
Check for Spark
Check for fuel
(guessing you've got them as it is attempting to fire)
Pull cam covers and check overlap positions for each cams in relation to each front cylinder TDC
Afraid it's now a case of double and re-checking everything you've done so far.
Aye, thanks guys. Thought that was the case, just needed it confirming/didn't want to believe it! lol
Will start disassembling the engine tomorrow!
Was sure I got the cam timing right, as I say I double checked it a number of times as not only did I want to get it wrong and bend/smash something, but I didn't want to have to got through what I'm about to do!
Will start disassembling the engine tomorrow!
Was sure I got the cam timing right, as I say I double checked it a number of times as not only did I want to get it wrong and bend/smash something, but I didn't want to have to got through what I'm about to do!
Long shot but easy to do is the battery, when mine was on the way out it used to turn over fairly well but always die as soon as it tried to fire, almost like the engine seized at the catch moment some times with a little pop at that point too. If it's not a new battery its worth a shot imhe.
Gray_101 said:
are you sure youve checked your cam timing right ? when your front piston is at TDC on either bank, the valves should be on over lap on the back piston on the same bank. ( i hope that makes sence )
Hello, Are you sure that's right? Thought it was 1 and 8 on overlap meaning it would be the back piston (8) on the drivers side and front (1) on the passenger bank?
Just been through getting this wrong ourselves!
Duncan
I think Gray is right. First you get piston 2 to TDC (which means 8 will be at TDC too), and the valves for piston 8 should be at overlap and it's these valves you set up. Then you get piston 1 to TDC (which means 7 is also at TDC), and set up valves on 7. You do even bank first then the odd bank so that you keep the tension on the chain on the adjuster side.
Best post I've seen on Cam timing by James:
Hi Jammy
Hopefully I can help a bit with this one.
1. Use the full timing chain cover to locate the gears and tension the chain. You'll be taking it on and off a few times and soon get used to removing / refitting it whilst holding the chain tight with a spare hand! If you have got the timing close enough, you be making minor adjustments by slackening the bolts on the end of the cam and moving it within the slotted part of the gear.
2. In short yes - you need to remember that in effect you are timing two 4 cylinder engines. Therefore, initially you just get it close-ish by setting up equal overlap when the engine is between the two TDCs but then you have to adjust the cams so that the relevant cam has the correct timing when each bank is at TDC. IE - firstly, when 2 is at TDC, you set the cam timing for valves 7&8 before moving the crank round so that 1 is at TDC and you can set up the cam timing for valves 1&2. It's important to repeat this several times to check that the timing is right once the engine has been turned over a few times and the chain has found it's natural tension.
Regarding the fact that the book recommends the inlet valve being 1.5 mm lower than the exhaust valve; it would appear to be commonly accepted amongst those who know (Joo, TVR Power, APS) that it is better to set the cam timing up as equal overlap as the engine runs better and makes more power. It's also easier to set up this way... To check when I had got the overlap equal I used a metal set square held against the side of the cam which was broad enough to cover both cam followers. If you can position a light behind this it's very easy to see how much light shines through the gap between the cam follower and the set square an adjust the cam accordingly.
If you've got the same manual as me, that TVR "mechanic" isn't adjusting the cam, he's hitting it with a big mallet to try and get it to move - you are right with your assertion that you are setting up TDC 2 with valves 7&8 and TDC 1 with valves 1&2. Rather than hit the cam with a hammer, I found it rather easier to use a long steel bar with two M5(?) bolts though which where spaced to coincide with bolts which hold the cam gears on - that way, when you loosen the cam gear you just have to use the lever to tweak the cam position whist the gear remains still. If you need to make any bigger adjustments, I found it easiest to pull the timing chain cover off and move hop the chain over by a tooth.
I am convinced that cam timing is critical to making good power - so make sure you get it right! Good luck!
That'd suggest piston 1 at overlap for the odd bank?
Thread here: http://www.pistonheads.com/gassing/topic.asp?h=22&...
Regards
Duncan
Hi Jammy
Hopefully I can help a bit with this one.
1. Use the full timing chain cover to locate the gears and tension the chain. You'll be taking it on and off a few times and soon get used to removing / refitting it whilst holding the chain tight with a spare hand! If you have got the timing close enough, you be making minor adjustments by slackening the bolts on the end of the cam and moving it within the slotted part of the gear.
2. In short yes - you need to remember that in effect you are timing two 4 cylinder engines. Therefore, initially you just get it close-ish by setting up equal overlap when the engine is between the two TDCs but then you have to adjust the cams so that the relevant cam has the correct timing when each bank is at TDC. IE - firstly, when 2 is at TDC, you set the cam timing for valves 7&8 before moving the crank round so that 1 is at TDC and you can set up the cam timing for valves 1&2. It's important to repeat this several times to check that the timing is right once the engine has been turned over a few times and the chain has found it's natural tension.
Regarding the fact that the book recommends the inlet valve being 1.5 mm lower than the exhaust valve; it would appear to be commonly accepted amongst those who know (Joo, TVR Power, APS) that it is better to set the cam timing up as equal overlap as the engine runs better and makes more power. It's also easier to set up this way... To check when I had got the overlap equal I used a metal set square held against the side of the cam which was broad enough to cover both cam followers. If you can position a light behind this it's very easy to see how much light shines through the gap between the cam follower and the set square an adjust the cam accordingly.
If you've got the same manual as me, that TVR "mechanic" isn't adjusting the cam, he's hitting it with a big mallet to try and get it to move - you are right with your assertion that you are setting up TDC 2 with valves 7&8 and TDC 1 with valves 1&2. Rather than hit the cam with a hammer, I found it rather easier to use a long steel bar with two M5(?) bolts though which where spaced to coincide with bolts which hold the cam gears on - that way, when you loosen the cam gear you just have to use the lever to tweak the cam position whist the gear remains still. If you need to make any bigger adjustments, I found it easiest to pull the timing chain cover off and move hop the chain over by a tooth.
I am convinced that cam timing is critical to making good power - so make sure you get it right! Good luck!
That'd suggest piston 1 at overlap for the odd bank?
Thread here: http://www.pistonheads.com/gassing/topic.asp?h=22&...
Regards
Duncan
jammy_basturd said:
I think Gray is right. First you get piston 2 to TDC (which means 8 will be at TDC too), and the valves for piston 8 should be at overlap and it's these valves you set up. Then you get piston 1 to TDC (which means 7 is also at TDC), and set up valves on 7. You do even bank first then the odd bank so that you keep the tension on the chain on the adjuster side.
This is correct! ^Its a flat plane crank so that when piston 1 is at TDC on the exhaust stroke, piston 7 is also at TDC but on the compression stroke. Hence you measure the overlap on rear piston of a bank when the front is at TDC with both valves closed.
The same is true of the even bank with pistons 2 and 8.
Edited by Tanguero on Monday 18th October 09:38
DuncanM said:
Bump for anyone else who would like to comment on this?
I was of the understanding that pistons 1 and 8 are 75 degrees apart (TDC) and the cams are set on these two pistons at TDC = equal overlap.
Anyone
.
Duncan
Pistons 1 and 8 are 75 degrees apart and on different banks, timing is set on one bank only at a time. I was of the understanding that pistons 1 and 8 are 75 degrees apart (TDC) and the cams are set on these two pistons at TDC = equal overlap.
Anyone
.Duncan
Timing should be set so that the rear piston of the bank has equal overlap (one valve opening the other closing) when the front piston on the same bank is at TDC with both valves closed. Both pistons are at TDC just at different points in their cycle.
The other bank will be 75 degrees away from TDC on the corresponding cylinders and should have the timing set separately using its front and back cylinders.
Good point, this topic does indeed say it should be 17-22 but then that is at idle.
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