Volvo 8.1 GI-B Puzzle!
03-27-2012, 12:39 PM
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Volvo 8.1 GI-B Puzzle!
Newbie here, need help!
I bought a used 2002 boat with Volvo Penta 8.1 GI-B engine. Serial number upon request.
Engine ran fine, then second season began occasional “skipping/shuddering” which eventually became constant.
WOT operating range is published as 4200-4600 rpm depending on prop. My boat normally operated at ~4250, now at 3900.
Had fuel injectors professionally cleaned, tested and spray pattern checked and all are within spec.
Fuel rail cleaned.
New fuel pump assembly installed 7/2009.
Fuel filters changed, opened and found clean. New filter sealed with aircraft gasket sealer.
Checked exhaust temp sensors and oil pressure sender. No fault codes set. Engine not in “de-rate mode”.
Spark plugs and spark plug wires replaced.
Grounds to block and ECU checked.
New series 31 battery.
PCV valve checked.
Fuel pressure normal, no drops at WOT.
Cylinder drop test with Volvo computer shows cylinder number 8 is the culprit. No/very little change in rpms when dropping fuel to number 8.[/B]Compression test normal. Leakdown slightly low on #8, but within spec.[/B]Swapped injectors with another cylinder, but # 8 still affected.
Swapped spark plugs and wires with another cylinder, still #8.
Swapped coil pack with another cylinder, still #8.
“Noid light” tested fuel injector wiring harness on #8 and appear to be triggering normally.
Pulled head, replaced valves and seals. No visual defects found. Reinstalled w new gaskets.
Checked push rods, found to be straight.
Checked common ground in wiring harness, no intermittent grounding issues found.
Fresh 91 octane no-ethanol fuel.
Ignition timing registering normal.
Could this be the ECU? Any leads on an aftermarket testing/programmer?
I bought a used 2002 boat with Volvo Penta 8.1 GI-B engine. Serial number upon request.
Engine ran fine, then second season began occasional “skipping/shuddering” which eventually became constant.
WOT operating range is published as 4200-4600 rpm depending on prop. My boat normally operated at ~4250, now at 3900.
Had fuel injectors professionally cleaned, tested and spray pattern checked and all are within spec.
Fuel rail cleaned.
New fuel pump assembly installed 7/2009.
Fuel filters changed, opened and found clean. New filter sealed with aircraft gasket sealer.
Checked exhaust temp sensors and oil pressure sender. No fault codes set. Engine not in “de-rate mode”.
Spark plugs and spark plug wires replaced.
Grounds to block and ECU checked.
New series 31 battery.
PCV valve checked.
Fuel pressure normal, no drops at WOT.
Cylinder drop test with Volvo computer shows cylinder number 8 is the culprit. No/very little change in rpms when dropping fuel to number 8.[/B]Compression test normal. Leakdown slightly low on #8, but within spec.[/B]Swapped injectors with another cylinder, but # 8 still affected.
Swapped spark plugs and wires with another cylinder, still #8.
Swapped coil pack with another cylinder, still #8.
“Noid light” tested fuel injector wiring harness on #8 and appear to be triggering normally.
Pulled head, replaced valves and seals. No visual defects found. Reinstalled w new gaskets.
Checked push rods, found to be straight.
Checked common ground in wiring harness, no intermittent grounding issues found.
Fresh 91 octane no-ethanol fuel.
Ignition timing registering normal.
Could this be the ECU? Any leads on an aftermarket testing/programmer?
03-27-2012, 11:35 PM
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What were the leak down numbers on #8? Did the #8 cylinder bore show any unusual wear maerks ro scratches compared to the other 3 cylinders under that head removed?
What was the tested compression on all cylinders and #8?
Try swapping one of the ignition coils between lets say #6 and #8 cylinder and see if the drop cylinder test issue moves to #6.
I would also look to get your boat's prop reworked after you get all cylinders running correctly to get the rpms up to 4600rpms minimum as you are definitly lugging the engine at 4200 rpms and that will damage the engine! The Volvo 8.1GI-B is rev-limited at 4900 rpms and Mercury runs the same 496Mag engine to 4950rpms for a rev-limit on the 375HP engine.
Best Regards,
Ray @ Raylar
Best Regards,
Ray @ Raylar
What was the tested compression on all cylinders and #8?
Try swapping one of the ignition coils between lets say #6 and #8 cylinder and see if the drop cylinder test issue moves to #6.
I would also look to get your boat's prop reworked after you get all cylinders running correctly to get the rpms up to 4600rpms minimum as you are definitly lugging the engine at 4200 rpms and that will damage the engine! The Volvo 8.1GI-B is rev-limited at 4900 rpms and Mercury runs the same 496Mag engine to 4950rpms for a rev-limit on the 375HP engine.
Best Regards,
Ray @ Raylar
Best Regards,
Ray @ Raylar
Last edited by Raylar; 03-27-2012 at 11:37 PM.
03-28-2012, 08:35 AM
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Wow, thanks for the ideas!
We tried the coil swap and still pointed to #8.
I don't have the specific compression and leakdown numbers, but the shop said it was within spec. Volvo tech rep said pull the head anyway so we did, replaced valves, seals and gaskets. They said leakdown improved. Not sure about compression. No mention of cylinder scratches.
I've considered re-propping but wanted to get the engine issue sorted first to make best decision on props.
I'll definitely check the fuse box main wire!
I may have to pull and completely disassemble engine, check cam and lifters if all else fails.
How do you check for blow-by?
I don't have the specific compression and leakdown numbers, but the shop said it was within spec. Volvo tech rep said pull the head anyway so we did, replaced valves, seals and gaskets. They said leakdown improved. Not sure about compression. No mention of cylinder scratches.
I've considered re-propping but wanted to get the engine issue sorted first to make best decision on props.
I'll definitely check the fuse box main wire!
I may have to pull and completely disassemble engine, check cam and lifters if all else fails.
How do you check for blow-by?
03-28-2012, 09:44 AM
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Sorry, I missed the coil swap listed. What were the fuel pressures at idle and at WOT when tested.
Any good shop knows to write down the compression and leak down numbers to give to the owner and keep on their work order for future reference.It really important to know what they were on that cylinder to identify whether cylinder pressures are a problem or not. I would hope that the mechanic would have noted any cylinder wall damage in that cylinder or others on that side and normally we take pictures with a digital camera for records and use.
If the shop has not written down the compression and leakdown numbers they SHOULD redo them at THEIR EXPENS and get them to you for your use.!
It is not necessary to pull the engine to check a camshaft for example as they can pull a valve cover and with a dial indicator they can measure valve lift on the tops of the pushrods in that cylinder and then meausre an adjacent cylinder.
Simple blow by meaurment on an 8.1L engine is to remove the oil fiill cap and observe the vapor coming out at idle them rev the engine and see if it increases or goes away with some vacuum. It should go away on rev-up. The leak down numbers if in line now should indicate if blowbuy is an issue and when they took the leakdown measurements they should have alSo listened to the low cylinder and determined whether the air leaking was in the intake tract, exhaust tract or in the crankcase.
Best Regards,
Ray @ Raylar
Any good shop knows to write down the compression and leak down numbers to give to the owner and keep on their work order for future reference.It really important to know what they were on that cylinder to identify whether cylinder pressures are a problem or not. I would hope that the mechanic would have noted any cylinder wall damage in that cylinder or others on that side and normally we take pictures with a digital camera for records and use.
If the shop has not written down the compression and leakdown numbers they SHOULD redo them at THEIR EXPENS and get them to you for your use.!
It is not necessary to pull the engine to check a camshaft for example as they can pull a valve cover and with a dial indicator they can measure valve lift on the tops of the pushrods in that cylinder and then meausre an adjacent cylinder.
Simple blow by meaurment on an 8.1L engine is to remove the oil fiill cap and observe the vapor coming out at idle them rev the engine and see if it increases or goes away with some vacuum. It should go away on rev-up. The leak down numbers if in line now should indicate if blowbuy is an issue and when they took the leakdown measurements they should have alSo listened to the low cylinder and determined whether the air leaking was in the intake tract, exhaust tract or in the crankcase.
Best Regards,
Ray @ Raylar
03-29-2012, 07:15 AM
#7
coolrunning racing
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I read here somewhere about a lean condition on one cylinder having to do with being at the end of the fuel rail were air bubbles accumulated. Food for thought.
03-29-2012, 08:11 AM
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Talked to the svc mgr at the shop and shared some of the ideas I've received. He was open to all suggestions. He did have the compression and leakdown numbers but I didn't write them down. They did those tests twice to be sure they were accurate.
Regarding cylinder scratches he said there were still cross hatches on the cylinders. I asked if that might mean frozen rings, he said no, if rings were frozen there would probably been oil in the cylinder, fouled plug, etc.
He said he'd check the fuse block wiring.
The dial indicator check makes perfect sense to check cam lobes.
Coincidentally the tech said he was wondering if #8 was getting enough fuel, didn't mention if spark plug showing lean condition, but that could match up with the bubble in fuel line comment.
I'll call him again today. Thanks for your time!
Regarding cylinder scratches he said there were still cross hatches on the cylinders. I asked if that might mean frozen rings, he said no, if rings were frozen there would probably been oil in the cylinder, fouled plug, etc.
He said he'd check the fuse block wiring.
The dial indicator check makes perfect sense to check cam lobes.
Coincidentally the tech said he was wondering if #8 was getting enough fuel, didn't mention if spark plug showing lean condition, but that could match up with the bubble in fuel line comment.
I'll call him again today. Thanks for your time!
03-29-2012, 08:18 AM
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Just talked to svc mgr. Didn't see any corrosion or abnormalities in fuse block wiring. Svc mgr thought the fuel rail would probably self bleed through the injectors. I asked him to check valve lift. They recorded injector pulse widths and sent to Volvo tech rep. Volvo rep said he'd be here Tuesday to look at the boat. Guess I'll wait and see what he recommends.
Last edited by ChickenSteve; 03-29-2012 at 08:21 AM.
