tr6tuga Posted December 4, 2015 Report Share Posted December 4, 2015 Knowledgeable forum! My quest for finding the erratic picking up is driving me nuts! It's a 1971 PI Electrics all check no voltage drops all across battery and fuel pump Dizy, leads, spark, timming check New valves set, head gasket, valve clearance rest Compression test less than 5% variation Fuel line, all check, clean tank, new / refurbish lucas pump, PRV, MU, injectors, fuel hoses Fuel pressure at PRV and MU 110 psi constant. After a looong time bleding the lines finally got the six injectors cone spraying. Engine starts a firts runs unenven, them as soon hits the trotle it starves. After several attemps it sudendly runs perfectly all across the rpm range. Well, thought that found the balance after a full work day, whent for a beer:-) next day, all back to the same fuel starvation Previously trotle was balanced, manifold depression 7-8 hg Somehow the manifold depression is dwingling and the MU has wrong readings? Im missing something? It looks as soon the buterflyes open there is'nt enough depression and the MU shuts fuel supply? My vacuum tester needle goes from steady 7-8 hg to erratic when trottle Please some hints were to look Jose Quote Link to post Share on other sites
Nick Jones Posted December 4, 2015 Report Share Posted December 4, 2015 Are you sure it is not going rich rather than starving? MU increases fuelling as the manifold pressure rises (gets closer to atmospheric pressure). What about the choke lever? Is this returning fully? Nick Quote Link to post Share on other sites
John L Posted December 4, 2015 Report Share Posted December 4, 2015 I would check to see that all the butterflies all open at the same time, and have you checked the airflow on all of the separate inlets? What timing position have you set? If you use a bit of choke when setting off does it improve? What grade of fuel are you using? John Quote Link to post Share on other sites
Peter Cobbold Posted December 4, 2015 Report Share Posted December 4, 2015 (edited) Could be the fuel cam follower sticking. It should normally drop down when the manifold goes to atmospheric when throttles are opened, controlled by the diaphragm. Spray some WD40 inside the rectangular plastic cover on the MU. And try sucking and blowing down the hose from the manifold to MU, to help free the mechanism. Peter Edited December 4, 2015 by Peter Cobbold Quote Link to post Share on other sites
astontr6 Posted December 4, 2015 Report Share Posted December 4, 2015 Hi Jose, Vacuum is low? Why did you have to bleed injectors? What were the compression figures, s/b around 180 t0 185psi warm engine full throttle? Answers please, Bruce. Quote Link to post Share on other sites
tr6tuga Posted December 4, 2015 Author Report Share Posted December 4, 2015 Nick Definettly starvation, plugs dont get fouled wit petrol smell, and after a minute pause engines starts at first turn them faisl (petrol left overs) Sucking/blowing vacuum hose no response at all Vacuum recheck, steady at idle 7-8 hg, erratic when trottle up but due to a stumbling engine Choker lever is returning fully John Butterflies all open at the same time Air flow checked and ballanced Choke, no improvement Timming 10º btdc Peter WD40? I don´t whant to use it on a newly refurbished MU by Prestige, agree with you, it's pointing to some sticking on the MU Fuel pump with independent power supply no difference at MU, allways constant, static, idle, 2000 rpm Bruce Compression test done previously all within 5% variation, no dimensions sorry Had to bleed the injectors and took a long time, feel the pulse but only droplets...them sudendly nice cone on all... Give up ! returning MU to Prestige Thank you Quote Link to post Share on other sites
Steves_TR6 Posted December 5, 2015 Report Share Posted December 5, 2015 (edited) Hi Jose, hope all's well in Porto? Amita is in Barcelona this winter, a lot less wind there than the Atlantic coast! Aside from fuel possibilities, I wonder about ignition.. Many years ago a similar saga was traced to a faulty condenser, and on another occasion to a wire in the distributor that had rubbed and was erratically earthing. Now I always change the cheap stuff first! Regards Steve Edited December 5, 2015 by SDerbyshire Quote Link to post Share on other sites
Peter Cobbold Posted December 5, 2015 Report Share Posted December 5, 2015 , I wonder about ignition.. Many years ago a similar saga was traced to a faulty condenser, and on another occasion to a wire in the distributor that had rubbed and was erratically earthing. Now I always change the cheap stuff first! Regards Steve +1 Also check the wire from the loom to the coil. I had it fail so that engine rock killed the ignition. Remaking the connector cured it. Peter Quote Link to post Share on other sites
tr6tuga Posted December 9, 2015 Author Report Share Posted December 9, 2015 Steve Glad to ear from you, Barcelona is a great place for winter, but can be very cold:-) electrics was from where I started, and sistematic parts replacing. Peter As per above that flimsy wire was checked, I m convinced is the Mu it does look a sticking cam folower, no reation sucking/blowing the MU Keep updated Quote Link to post Share on other sites
tr6tuga Posted December 26, 2015 Author Report Share Posted December 26, 2015 Just as promised a update Had the MU back to prestige and back all in shappe no problem. I'll Try the ignition circuit, alternator, coil leads... Maybe 2016 will give a new push to my tr:-) happy seasons Jose Quote Link to post Share on other sites
jobster Posted December 27, 2015 Report Share Posted December 27, 2015 Nick in the fuel line? Tank breather blocked? Sounds to me something between tank and MU. Quote Link to post Share on other sites
barkerwilliams Posted December 27, 2015 Report Share Posted December 27, 2015 (edited) Jose, I have a 1970 pi and your symptoms are familiar. On reading your thread I note that you have checked the butterflies are opening at the same time. How did you do that? If it is by eye or feeler gauge, but that is only a rough guide. Have you used one of these - a Dellorto carburettor tuning gauge - ebay about £35? To get a good tickover and pickup you need a balanced airflow. These gauges fit directly into each throttle body and indicate the "sealing" of the butterfly. It is amazing how each butterfly seems to be closed and sealed but there is a wide variation in airflows passing the "closed" butterflies which can be then be adjusted out. Once adjusted the simultaneous opening of all butterflies can be adjusted on the throttle linkage. The throttle is opened slightly - perhaps 1200 revs with a screw on the throttle linkage then again the gauge is used to get the same airflow, i.e. the same butterfly opening on all six cylinders. Once adjusted correctly all cylinders will be pulling together. The readings from these gauges is not important, it is just that all cylinders are equal. Alan Edited December 27, 2015 by barkerwilliams Quote Link to post Share on other sites
bluebob Posted December 28, 2015 Report Share Posted December 28, 2015 Hi Jose Had a friend had the same issue after checking and rechecking I found the issue was a the feed between the tank and filter had collapsed slightly , so showing all the correct pressure`s etc then when fired up had the fuel starvation , check for blockage between tank and filter I assume the filter is ok? hope this helps Bluebob Quote Link to post Share on other sites
tr6tuga Posted January 17, 2016 Author Report Share Posted January 17, 2016 Good morning knowlageble forum Got thr MU back from prestige, and once in place what a difference:-):-):-) It looks that the main issue was the MU uneven balance. The Tr never pulled so strong:-). But after a couple of miles, 50, rough pulling again but this time all over the range. Plugs out, 1,2 ok, 3456 sooted, so now carefuly balance the throtle with car balancer:-) Any good link besides the usual BB and Haines? Well the good part is that after almost a year strugling my TR knowledge is better:-) thnk you for all the help Jose Quote Link to post Share on other sites
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