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diesel to petrol conversion gone wrong


k-claw71
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Hi guys

Just joined as I have a problem with my 1.7sdi lupo. Me and a friend did the conversion all last week and got it running Sunday.

Started up first time so I jumped in but after about 2 miles it started to bog and even with my foot to the floor it still wouldn't run.

Any way my mate can't find any thing wrong, any advice?

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LOL, sounds like you just put petrol in a diesel to me.

But ok, you changed the engine, but what else did you change? What else didnt you change? Things like the fuel tank, or in tank pump?

Question: Why?

2nd Question: How? what did you do?

also, going from your OP it sound like you fired it up and then immediately drove off around the roads, why not leave it running on the spot for several minutes at least while double checking you havent forgotten anything and to see what it does?

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So, fuel delivery and metering is achieved how?

Compression ratio is over double that of a petrol engine, how are you controlling pre ignition and the resulting melted pistons or other damage?

How are you delivering and timing ignition?

I would think if you are able to make this run for several minutes then you are able to trouble shoot it and work out the problem, after all there is a mountain of tech problems that you have had to resolve to do this already isnt there?

It's probably used all the diesel in the lines and filter and then burned petrol until it died. Not sure why you declared it until you'd tested it properly tbh.

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apologies for the last post, I remember being young and enthusiastic too and trying some crazy stuff, some worked some didnt, like putting a 1275 head on an 850 mini engine when i was 17, it ran like a dog because i'd just decreased the compression ratio with the big combustion chamber on the 1275 head (doh).

The sheer effort of making a diesel engine run petrol is not worth bothering with, they are fundamentally different. One is a compression ignition engine the other is a spark ignition engine.

If you wanted more power from the sdi with undeclared mods, you probably could have messed with the pump fuelling and run 5% petrol in the diesel fuel to boost it a bit.

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19.5:1

i thought it would be a bit higher LOL

The diesel pump will disintegrate after having petrol thru it for enough miles as it needs the diesel for lubrication, so that is a non starter using that for fuel delivery.

Edit: I was going to say the same thing, pics or it didnt happen....

Edited by Sausage
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Hmmm

Let me see if i've got this right.

You and your mate added a lift pump to an SDI ( Suction Diesel ) then bypassed the timer so the glow plugs are on all the time, then drove it 2 miles on a mixture of Diesel and Petrol, when it stopped

1/ Diesel pump hates petrol seals etc and it can't inject enough petrol to get a mixture that will burn in the cyclinder anyway

2/ glowpugs are designed to work for a few seconds no more so they are probably burned out.

I hope this is wind up, if not you and your mate are too dangerous be alllowed anywhere near mechanical things

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We already though about the pump, we are running two stroke oil to help it. Pumps fine and we added the extra pump so it can meet the fuel demand.

Glow plugs arnt on all the time they fire intermittently like spark plugs.

I'm pretty sure this is just the diesel lambda not being set up for petrol

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Exactly that, sparks are there to ignite at a specific time, glow plugs don't go hot/cold/hot/cold quick enough to ignite the fuel at the right time, Itl be totally random, no wonder it runs like a bag of bolts.

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