turbo taylor

iTrader: (2)

looking for a bit of help if possible

just done a compression test on my cossie and the results are as follows

no 1 110 psi
no 2 120psi
no 3 120 psi
no 4 120psi

would this make the car run lean top end

also would it make a difference if it has low comp pistons

many thanks

tabetha

Low comp pistons will give a lower reading than higher comp pistons.
The compression pressure has no relationship to the fuel mixture, assuming it has the correct chip/mapping to suit.
tabetha

botters

iTrader: (2)

allthough ive never done a compression test on a low comp cossie i must say those readings look a bit low to me i could be completley wrong tho lol!

turbo taylor

iTrader: (2)

thanks for your reply mate

the car has been running like a bag of shit lately i was book into msd later this month but have now cancelled that due to checking this out tonight because i thought it was engine rebuild time which i cant believe has happened because the engine was rebuilt 12000 miles ago but the car was running 2 bar of boost for 374 bhp.

the symptoms that lead us to believe the rings may be done are the car runs like a bag of shit it was misfiring like mad when on boost i had it on rollers on monday but im not too keen on the place i took it to any way what i got told from them was it looks like a needed a new map sensor because the fueling was all over the place running rich on idle then running lean on boost but when it came on boost it was up and down but running lean. they ended up setting it up at 19 psi peak boost and holding 17 and it gave the car 256 bhp on a stage 3 setup they also told me that they would give it more fuel to try and eliminate the lean mixture at top revs.

so before i tarvelled all the way to blackpool to get it looked at me and my brother in law decided to start checking things over which the first port of call was the pressure in the bores and that how i think it needs a rebuild maybe just new rings i dont know but im looking to see what the bores should be at with low comp pistons to try and get things sorted out

tabetha

It doesn't need a rebuild at all, did they even bother to check the fuel rail pressure ?
It sounds like a classic fuel pump failure to me, these will surge violently sometimes, I've just replaced my own pump for the same reason, it was surging from 0.5 bar to just over 3 bar, absolutely rythmically idle was going from around 500rpm to 2500rpm, the pump sounded 100% PERFECT, it was not until I put the gauge on there that I confirmed my suspicion.
Your readings are all around the same, no1 is a bit low in comparison, but could just be a simple error with the tester.
DON'T take the engine apart, check your fuel pressure, renew the pump/filter, rewire it and the fans also if not already done so.
tabetha

turbo taylor

iTrader: (2)

the bit where you say about the idling the car has had a mind of its own twice in the last week it started revving from normal idle and jumped up to 2000rpm then a couple of days ago before i went to take it to the rollers i had just put fuel in her then when i started it again it started idling at 3000 rpm switched her of and it was back to normal. ill get the fuel pump checked tonight but i do have a loom already run in for it, it was a new pump last year and i also have a new filter sitting around. what should the pump voltage be at on idle and then under load?

thanks for your help mate

tabetha

Ideally you want within around 0.5 volt of the battery voltage, was the earth new on the pump as well ?, the voltage should be the same under full load, this can be easily watched for on the rollers, the only thing that will increase under full load will be the amps used by the pump, this will if you have a bad connection/joint etc cause a major volt drop, but not if all is good wiring connection/joint wise.
Your idling may just be a dicky iscv, but something is telling it to raise to that amount, normally on the std ecu's it's the TPS reading.
For some reason these bosch pumps don't seem to like any time idle, mine was perfect when laid up for engine build, but decided it had enough, and surged like buggery up and down pressure wise, not very impressive at all for what is a expensive pump, if, or rather when it goes again it certainly won't be a bosch one going back on there, I'll be running twin walbro's, work out same price but hopefully better quality/longevity.
Mine was 2 years old, no debris problem, tank is brand new as is filler and all pipes.
I check the fuel pressure is not fluctuating, and if not within say a year old replace fuel filter, before having it set up/rollered I'd replace the CTS also.

turbo taylor

iTrader: (2)

right a bit of progress has been made yesterday

so started checking over things last night and found that the fuel pump was the fault of the fueling had a volt meter on it and when the ignition was turned it was 3.5 for a split second then down to 1 volt so that has now been rewired and getting the ful 12 volts now

next was the misfire and i have traced that to the multi plugs under the scuttle panel sprayed wd40 into them and the car ran so much better still a misfire there but a big improvement on what it was

can any one tell me exactly what each of the 3 plugs do im going upto an auto electrician today to get a quote for changing the plugs over for new and see maybe about getting the wires joined and do away with the plugs altogether but that is the last resort.

ill also get them to have a look at the new fuel pump wiring to get that done properly also.

cheers for your help tabetha greatly appreciated

tabetha

At least it wasn't the pump itself causing the surging, just it's supply.
So long as you can solder it is easy to replace the three multi plugs, the 2wd doesn't use these to start with, soldering is not hard to master, and in your location you have access to one of the best solder fluxes you can have/use, PINE TREE RESIN, this cleans wires beautifully, just scrape some off a tree, use this as the flux when soldering.
There's how to's on here re the fuel pump rewire(pf) you are talking to do all the pump rewire, fan rewire(if not already done) and the multi connectors soldered about £50, and that includes a decent soldering iron and loads of spare wire left over.
When I rewired my pump, I used a relay holder, about £3 to mount the new relay behind the seat upright on the nearside inside the boot, there is already a 8mm hole so ideal for a 6mm nut/bolt to hold there, this has several advantages, security, at shows etc simply pull out the relay, to stop fuel pump, if having any trouble you can simply bridge 30(input from battery via fuse) to 87(output to pump) so it will run all the time, very useful for diagnostic work etc, or if relay packs up you're not stranded.
A pump rewire kit is typically £45 on it's own, and a 2 year old could do it tbh, the last kit I fitted was not even fused at the battery, despite being a so called "proper" loom, some wires were way too short, others way too long.
tabetha