Attention: Analytical Minded 75/ZT Techies. Amateur Diagnosis incoming... :-) - Forums
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post #1 of 4 (permalink) Old 29-04-2017, 00:11 Thread Starter
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Question Attention: Analytical Minded 75/ZT Techies. Amateur Diagnosis incoming... :-)

Decided to get my MG6 Engined MG ZT-T 1.8T running and off SORN. Been SORN unused for eighteen months now. Bought saving it from scrapyard fate after previous owner had a travelling K-Series specialist remove the cylinder head. Decided not to repair and I bought car with its cylinder head and all removed parts in Tourer loadspace towing it home like that. Here it is on arrival home :~

Previous owner drained tank of several gallons of fuel via the In-Tank Fuel Filter Access Panel when it looked likely car off to breakers. So one of the first tasks was to reassemble that which was in a bit of a state. Sometime later with original headless engine removed and MG6 engine in place, started MG6 engine and ran it for a few seconds to confirm it was a runner. Very hesitant to start but, fired up after a few seconds. Started occasionally in the meantime and again hesitant or non-start. When start failed got it running by squirting a few drops of RON 75 into the Inlet Manifold via the Brake Servo Vacuum Tube take off. That results in immediate start. Past couple of days, I have completed 99% of the reassembly of all removed parts and charged and bled the cooling system with 50-50 OAT Coolant. It did start then but again only with a squirt of RON 75 into the Inlet Manifold. Engine then runs smoothly and warmed up nicely with strong heater output too. Always a good sign that for me.

Then, on fully warmed engine switch off, car would start immediately every time whilst warm. However, if left to cool, it would not start only with a squirt of fuel.

So based on this scenario which has been happening over the past few days, my automotive amateur analytical mind now believes that any residual pressure in the fuel lines in the warm engine will enable the engine to start every time. When allowed to cool say overnight, needs a squirt of RON 75 to start. So it looks like the fuel pressure is being lost as the engine cools.

So, a quick look into the In-Tank Fuel Filter will be necessary. Which as far as I know was the only part disturbed when removing the fuel previously by the then owner.

So, from the above description, a question for those far more experienced in these matters than I. Have I correctly identified the problem is the In-Tank Filter needing attention or, is the Fuel Pump the guilty party here? Maybe both...

In any event, I will disassemble the In-Tank Filter and fit a new large O-Ring and Clip. If that does not do the trick then The Pump may be the guilty party after all.

Any thoughts on this will be appreciated before I look at the Fuel Supply issues more closely.

Thanks in advance.

Apparently ... in a parallel universe MGJohn drives .........A.......

B>>M>>W ....

Arrrrrggghhhhh......... ......
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post #2 of 4 (permalink) Old 29-04-2017, 08:31
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It might be what I call incipient FFS. The filter module leaks just enough to inhibit starting from cold, but once started (using an independant fuel), the engine runs. I suspect it would be problematic to actually drive at any speed. Don't know if you tried that. I'd suggest that any work done on the filter module, even lifting it so far out of the tank is enough to cause slackening, especially if the forces causing it have bee acting positively for some time.My gut feel is tis will resolve wen you fit a FOC. I'd also agree about renewing the rubber oring, which will probably have dried out during the long stand without fuel

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post #3 of 4 (permalink) Old 30-04-2017, 11:07
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Agree fuel filter worth checking/ renewing. Tbh could be other stuff eg weak sparks. Engines start better when warm.

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post #4 of 4 (permalink) Old 02-05-2017, 00:55 Thread Starter
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Location: Gloucestershire - Cotswold Cockney
Car: MG Montego Turbo; 620ti x3; MG ZS; MGF and MG ZT 1.8t x2; MG ZT-T x1
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Bank Holiday UPDATE :~


Late Monday Bank Holiday afternoon I removed the In-Tank Fuel Filter Assembly and saw Cap was correctly aligned. Fitted locking Clip in usual place. I lifted Filter almost fully out and saw the Fuel Gauge Sender Unit had become unclipped from the body of the Filter Assembly. To refit that I had to pull it out as far as I could. This revealed that the Scavenge Pipe ( the Blue Part on the lower component in Greeners picture ) here :~

....was also unclipped and thus detached from the body of the Filter. I suspect heavy handling by the PO when draining the fuel as at the time he believed the car was headed to the scrapyard. This also revealed that side of the fuel tank was near empty almost bone dry.

Took three 5 litre Plastic Fuel Cans to the petrol station and got 15 litres of RON's best 75.. Poured that lot into the almost empty Filter side of the tank, and using some Vaseline ( light thin smear a great help with fitting tight coolant and fuel seals ) then reassembled the whole assembly. The Vaseline made the job much less of a hassle than when doing this before on other ZTs.

Very fiddly job to reattach the Sender and Pick-up but, got there in the end using string as third hand.

So, plenty of fuel in the Filter side of the tank now but, no start on key. Although it almost did several times. I could not start the car and had to inject a small quantity of RON 75 into the Inlet Manifold via the Brake Servo Vacuum Tube fitment hole. Immediate start and engine ran fine. Started several times cold after switching off and allowed the engine to fully warm up. Started every time. Five hours later, engine fully cooled down, fingers crossed I twisted the key to operate the starter in the stone cold engine... It started.

Ever the doubting type needing confirmation, before pressing the submit button here, just popped out @ 01:40 ( bit chilly with plenty of stars in night sky ) and again, immediate start on key. Plus, the fuel gauge indicates 1/3rd full so despite the abuse of the In-Tank Sender Unit, that appears to be working fine too.

So, looks OK but I will check again before driving the car any distance.

Apparently ... in a parallel universe MGJohn drives .........A.......

B>>M>>W ....

Arrrrrggghhhhh......... ......
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