Who else can't get a simple motor to run properly ?

DoubleChevron

DoubleChevron

Real cars have hydraulics
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Hi All,

I thought I'd post here to see if anyone had any ideas about what is going on .... 'cos I'm scratching my head! A couple of weeks back the ****box rangie decided it wouldn't start (it had only been shut off for 5minutes while I picked up one of the kids).

It seemed to massively flood to the point where the car hydrolocked for a second after cranking for about 15seconds (in three five second bursts) ....I coulnd't get it started even though there seemed to be spark at the plugs. In desperation I unplugged the fuel pump (thinking maybe some injectors had stuck openO ... but still no go.

so went back the next day with fresh set of plugs to try and fire it up. It fired up very unhappily on gas. banging away on a hand full of cylinders ... So I drove it home banging away on probably 5 or 6 cylinders. Initially I thought something must have happened to flood the **** out of it. Now I'm starting to think the flooding was a side effect of something that broke/died when the car was shut off. It wets No 8 plug and sounded to miss all over the place "sort of". Its very hard to narrow down which cylinder is missing even by pulling the plug leads one at a time ( No 7 and No 8 seem to be the issue though)

I tried another set of plugs, checked the leads ..... Still crappy runinng on gas. In desperation I ordered in a compression gauge as I thought I must have damaged it when it hydrolocked (eg: bent conrods)


No 2: 135
No 4: 137
No 6: 137
No 8: 120
No 1: 140
No 3: 135
No 5: 135
No 7: 145

Low ... but certainly should run without any issues (well the gauge may read low to, it was only $23 delivered on ebay). So yesterday I checked all the HT leads, swapped the cap, rotor button, coil, ignition module with another car ... I even thought I better cover all bases and got No 1 at TDC .... made sure the rotor button was pointing and No 1 and checked the firing order (several times). It still sounds like its banging away on 6 cylinders and isn't happy. The only thing I haven't checked via substitution is the trigger wheel and sensor inside the dizzie. Does anyone have any ideas about what is going on here ? It seems to be No 7 and No 8 that don't wan't to fire. Given its running on LPG I completelly rule out issues with the fuel side ... it has fuel ... seems to have good spark ... has compression .... why no "bang" ?

I'm thinking its possible the cam timing moved when the motor hydro-locked. Does anyone know of a simple way of checking the cam timing? .......... I don't understand how it hydro-locking against the starter would hurt the valve train though .... both valves are shut on the cormpession stroke where the cylinder stops. The only thing I think this could do is cause a bent crank rod (which the compression check should show).

I'm rapidly running out of ideas here .... changing over the trigger wheel and sensor in the dizzie is my last desperate attempt to fix this (which I'm sure will make absolutely no difference
sad.gif
).

this afternoon I'll pull the rocker covers and check the valve operation .... and pull the dizzie back out and check the drive gear on the camshaft with a torch.... How can a simple petrol engine have me scratching my head like this :clown:

Oh, and I also checked the timing chain by rolling the motor forward and backwards .... there is no delay is movement of the rotor button... so in theory there is no slack/slop in the timing chain at all.

seeya
Shane L.
 
No help to you at all - but my diesel Landcruiser engine started running on 5 cylinders. It is now in bits - cracked piston. Engine rebuilder showed me hairline cracks in the other 5 😱.

Only positive is that it happened close to home - less than 200 km up the highway.
 
Armidillo said:
No help to you at all - but my diesel Landcruiser engine started running on 5 cylinders. It is now in bits - cracked piston. Engine rebuilder showed me hairline cracks in the other 5 😱.

Only positive is that it happened close to home - less than 200 km up the highway.
Click to expand...

Oh .... don't jinx me like that! My concern is I don't want to pull the motor down and spend hunreds/thousands on it to find ........ I needed a new $15 rotor button after all the $$$ and work :clown: :rolleyes:
 
Hi Shane :)
Sounds a bit unusual. My shoot from the hip suggestion is to look for a blocked exhaust 🥴
Jaahn
 
When you tested the spark plugs to see which cylinder wasn't working you said you had mixed results. I would chase that because your symptoms might indicate some bad spark plug leads (or at least you can't rule it out at the moment). Can you go back and try testing with a timing gun? Test each individual lead to see if the gun fires. Doesn't matter the timing just to make sure the plugs fire. If the gun doesn't fire, the spark plug doesn't fire. Much more reliable test than pulling the plugs. It will also show if one cylinder fires erratically.
 
is it sucking air in somewhere ,? rough running may have broken a vacuum line or somethings fallen off ,what do 7 and 8 have in common do they both pull from the same part of the manifold ,etc
 
"It wets No 8 plug and sounded to miss all over the place "sort of". Its very hard to narrow down which cylinder is missing even by pulling the plug leads one at a time ( No 7 and No 8 seem to be the issue though)"
Hi Shane :)
That statement above reminded me of working on a car not so long ago which had silly symptoms like that. It turned out to have a almost completely blocked CAT. But possibly a collapsed muffler or crimped pipe etc might give the same effect. Worth checking 🥴
Jaahn
 
Well I changed the pickup in the dizzie .... and the car started "as normal". ie: rather than cranking for 5seconds before spluttering to life, it now fires instantly again .... with a distinct heavy miss. So i changed the lead and plug on No 8 and tried again ..... and it wet the plug. So I put the compression gauge into that hole and fired it back up. Sigh ...... < 75psi tops ....
sad.gif
I've bent a conrod when it hydrolocked.... or damaged something. That's a shame ... given every other pot is near bang on 135psi .... this was a good motor!! (was
sad.gif
).
 
Hi Shane.

That's really frustrating.

Have you been able to confirm your hydraulic lock suspicion? From your first post you assume that the fluid is petrol. Assuming that you have the 3.95Lt V8 with 8.1:1 CR, it would take approximately 61ml of fluid to achieve this. That's a 1/4 of a cup of petrol, quite a lot to flow in via an injector.

I was wondering how you could obtain some sort of confirmation of your diagnosis, without partial disassembly of the engine. If the conrod has bent and you also have lower compression, then the assumption is that the piston is not rising to the same point at TDC for No 8 cyl, as it did prior to the hydraulic lock event, which would explain the lower compression of 75 PSI. While I am unfamiliar with the Rover V8 engine, could you use a piece of wire down the sparkplug hole to feel the uppermost position of the piston and then compare it to an adjacent cylinder? Alternatively if the overhead valves are in the same axis as the bore, could you place the No 8 Cyl piston at TDC and then manually push a valve down until it made contact with the top of the piston, take a reference measurement of the top of the valve stem, and then do the same and compare to another adjacent cylinder?
 
Whippet said:
Hi Shane.

That's really frustrating.

Have you been able to confirm your hydraulic lock suspicion? From your first post you assume that the fluid is petrol. Assuming that you have the 3.95Lt V8 with 8.1:1 CR, it would take approximately 61ml of fluid to achieve this. That's a 1/4 of a cup of petrol, quite a lot to flow in via an injector.

I was wondering how you could obtain some sort of confirmation of your diagnosis, without partial disassembly of the engine. If the conrod has bent and you also have lower compression, then the assumption is that the piston is not rising to the same point at TDC for No 8 cyl, as it did prior to the hydraulic lock event, which would explain the lower compression of 75 PSI. While I am unfamiliar with the Rover V8 engine, could you use a piece of wire down the sparkplug hole to feel the uppermost position of the piston and then compare it to an adjacent cylinder? Alternatively if the overhead valves are in the same axis as the bore, could you place the No 8 Cyl piston at TDC and then manually push a valve down until it made contact with the top of the piston, take a reference measurement of the top of the valve stem, and then do the same and compare to another adjacent cylinder?
Click to expand...
You could use this method that Whippet has suggested, but I would be using a leak down tester or at least making up an adaptor out of and old spark plug and air hose fitting.

Then bring #8 piston up to TDC on the firing stroke and put about 100 PSI of air into that cylinder. You will need to lock the motor which if its a manual put it in gear with the hand brake on or if its an auto put the auto trans into the park position.

You will then need to have a listen at the exhaust, the throttle body and also in the rocker cover for escaping air. You could also look in the radiator to see if there is any bubbles there too.

If there is no air escaping you then can assume that you have a bent conrod that has allowed the piston to move down the bore, lowering the compression.
 
COL said:
You could use this method that Whippet has suggested, but I would be using a leak down tester or at least making up an adaptor out of and old spark plug and air hose fitting.

Then bring #8 piston up to TDC on the firing stroke and put about 100 PSI of air into that cylinder. You will need to lock the motor which if its a manual put it in gear with the hand brake on or if its an auto put the auto trans into the park position.

You will then need to have a listen at the exhaust, the throttle body and also in the rocker cover for escaping air. You could also look in the radiator to see if there is any bubbles there too.

If there is no air escaping you then can assume that you have a bent conrod that has allowed the piston to move down the bore, lowering the compression.
Click to expand...
Great idea Col. You have reminded me that many years ago we had a device to diagnose cylinder leakage, using compressed air, with a flow regulator and pressure gauge, as you have described it.

I was also thinking yesterday when I wrote my reply that if hydraulic lock has occurred, it is likely that the piston rings may be broken and/or ring lands distorted. This may account for the poor oil control and wet spark plug insulators and electrodes, and consequent misfiring. Poor compression alone should not cause a misfire. There is still 75 PSI compression available.

PS: I am not sure that an Auto in Park will lock the engine.
 
Hmm Shane it is hard to see using the starter would bend a conrod. Hmm NO ! Also I am doubtful about getting enough fuel in one cylinder by the fuel injectors as has been calculated by Whippet.
I was not there to observe the lockup so I am guessing, but doing a leakdown test would be best if possible. Possibly the suspected 'lockup' was just a random firing of the fuel/air in the cyl as the ign pickup malfunctioned. It is also possible one of the valves has a bit of carbon under it or similar after that. With a V8 it is also possible one valve cam is worn away and not working well !!.Give it a run and then check it out.
Good luck Jaahn
 
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Thanks Guys,

yes, you are all echoing my thoughts. I'm going to pull the fuel rail as soon as I get some time and see if one (or more) of the injectors is stuck open (a risk when you run on gas all of the time).

I'll try measuring the piston height on each cylinder, it has "angled" plug holes, so the variability in measurement could be huge. I'll also pull the head off and see what is going on. It'll have to come off either way as there is nothing you can do to fix "whatever" the issue is without removing the head.

I do have anohter motor that I can fit, but I need to sort out what happened, as I don't want the same thing to happen to the other motor!

The shitbox has always started like the choke is fully out on a petrol motor when it fires on petrol. (I did find wiring issues to the temp sender both on both the fuel rail and main one as I've checked everything over the last week or so). The car did run fine once running on petrol

However it only fired for about 1.5seconds on petrol before flicking over to LPG. So I never really worried about it rich starting issue (yeah I know, I suck :clown: ).

Basically the pickup in the bottom of the dizzie must have died ( or partially died .... damn it) that night the car wouldn't start. As soon as I changed that (after changing everything else I could think of) the car suddenly was its normal self again (only its decided its a 7cylinder now)

what is confusing is why did the compression test show 120psi the first time I tried it ? I'm betting there was fuel sitting in the cylinder!
 
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the initial post says no8 has 120 now 75 ,were did that go , before you pull it apart get no 8 on tdc and check the valve clearances to determine if you have a stuck valve ,be interesting to see if some oil down the plug hole makes a difference ,dont forget to hold the throttle open when testing ,true you probably will have to take the head off but the more information you have the easier it may be to work out what happened so it dousnt happen again .pugs
 
jaahn said:
"It wets No 8 plug and sounded to miss all over the place "sort of". Its very hard to narrow down which cylinder is missing even by pulling the plug leads one at a time ( No 7 and No 8 seem to be the issue though)"
Hi Shane :)
That statement above reminded me of working on a car not so long ago which had silly symptoms like that. It turned out to have a almost completely blocked CAT. But possibly a collapsed muffler or crimped pipe etc might give the same effect. Worth checking 🥴
Jaahn
Click to expand...

Oh, thanks for this, I wasn't ignoring the suggestion ..... The car sounds rather, er, "throaty" at the moment due to only having a rear resonator fitted ....... that has rotted the bottom out over the last couple of months. I haven't been in a hurry to fix it. I've been enjoying the loud rumble (probably just as much as everyone else doesn't enjoy it :ROFLMAO: ). Boss women certainly seems to think its very embarrassing :clown:
 
pugwash said:
the initial post says no8 has 120 now 75 ,were did that go , before you pull it apart get no 8 on tdc and check the valve clearances to determine if you have a stuck valve ,be interesting to see if some oil down the plug hole makes a difference ,dont forget to hold the throttle open when testing ,true you probably will have to take the head off but the more information you have the easier it may be to work out what happened so it dousnt happen again .pugs
Click to expand...

That's what I want to know. the 75 is with the motor running. It take probably 5seconds of running to gasp its way upto 75psi. I'm wondering if there wasn't fuel flooding the cylinder when I originally tested it. (filing combustion space ... possibly sealing the rings)
 
DoubleChevron said:
That's what I want to know. the 75 is with the motor running. It take probably 5seconds of running to gasp its way upto 75psi. I'm wondering if there wasn't fuel flooding the cylinder when I originally tested it. (filing combustion space ... possibly sealing the rings)
Click to expand...
Could be broken rings on that #8 cylinder, do as I suggested in post #10, you will soon know
 
Maybe better to take this discussion to the Land Rover forum. Rangie
 
DoubleChevron said:
Thanks Guys,

yes, you are all echoing my thoughts. I'm going to pull the fuel rail as soon as I get some time and see if one (or more) of the injectors is stuck open (a risk when you run on gas all of the time).

I'll try measuring the piston height on each cylinder, it has "angled" plug holes, so the variability in measurement could be huge. I'll also pull the head off and see what is going on. It'll have to come off either way as there is nothing you can do to fix "whatever" the issue is without removing the head.

I do have anohter motor that I can fit, but I need to sort out what happened, as I don't want the same thing to happen to the other motor!

The shitbox has always started like the choke is fully out on a petrol motor when it fires on petrol. (I did find wiring issues to the temp sender both on both the fuel rail and main one as I've checked everything over the last week or so). The car did run fine once running on petrol

However it only fired for about 1.5seconds on petrol before flicking over to LPG. So I never really worried about it rich starting issue (yeah I know, I suck :clown: ).

Basically the pickup in the bottom of the dizzie must have died ( or partially died .... damn it) that night the car wouldn't start. As soon as I changed that (after changing everything else I could think of) the car suddenly was its normal self again (only its decided its a 7cylinder now)

what is confusing is why did the compression test show 120psi the first time I tried it ? I'm betting there was fuel sitting in the cylinder!
Click to expand...
Hi Shane.

So the engine is running now - yes? And the vehicle is drive-able - yes? The change of the ignition trigger pickup seems to have resolved the initial starting problem, and the repairs to the wiring loom for the temperature sender might resolve the over fueling at initial engine start.

I would defer removing the cylinder head at this stage, try to maintain the engine in a drive-able state.

My suggestion is to drive the vehicle for a few days to let things settle, then perform another dry/wet compression test to establish a new baseline to compare with your original compression test. Like others, I am interested to understand the initial 120PSI, reduction to 75PSI.
Dry with ignition off and WOT,
Wet the same but with a teaspoon of engine oil down sparkplug hole to seal the piston rings.

Happy New Years eve.
 
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Well, I think I'll head out and buy a lotto ticket .... If I can have two completelly seperate failures at the same time like this .... I must be the luckiest person around. So the igntion pickup had gone wonky so the damn thing would barely run ..... I was deseperate to figure out how it possibly hydrolocked though. I didn't want to destroy the other motor in the same way.

I whipped the fuel rail and and hooked the petrol pump back up. The meter told me there was twelve volts at the injectors. This is good. I can just hooked each injector to the battery and cycle the igntiion to ( 2 second fuel pump cycle when the key is turned)..... and see if each of the injectors is spraying .... all simply just leaking when under pressure...... I however didn't get that far. Instead I grabbed my 8 year old and said .... "here take a video of this ... no-one is going to believe me otherwise"

 
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