[fnqcairns]

Hi all this has me stumped but diesel engine diagnosis almost always does, I have read almost every injection related post on here without finding the same symptom explained.

For a while now (a few hundred km) I thought the GQ had a slightly out of balance front wheel/s, then last w/e when loaded up to go camping these unbalanced wheels got worse, then on the way home from the 300km round trip it felt like all 4 wheels were out of balance noticeably shaking us at highway speeds.

On way home after 100km at highway speeds we pulled into the sevo to fill up to find the problem had got worse over that portion of the trip now with noticeable surging/hunting at all throttle levels so the full tank made no difference, while out camping we did about 16 or so km of low range driving to get in and out without noticing the problem.

The surging is super quick at speed so feels like unbalanced tyres, when going slow around town it remains a constant on-off a couple time a second say but always accelerates through all while surging softly no matter the throttle setting.

After the trip I changed the CAV style filter but this made no difference, car is now idling lower as well threatening to stall so I am using the hand throttle to keep it running when idling, it seems to idle fine then.

Today going to check the gauze filter because I know I have one but after this I am stumped, an air problem is about my only real go to under the bonnet so ..what next?

Have checked out the cost of new injectors but the old girl up until this problem blew next to no smoke, started on a dime etc

First drivability problem in 16 or something years of ownership..knew this day would eventually come

 

[GQshayne]

Make sure your fuel tank breather is not blocked.

Air leaks as you mentioned. Filter head primer is often a culprit.

No experience with fuel cut solenoid failing myself, but this is worth looking at too.

 

[fnqcairns]

Make sure your fuel tank breather is not blocked.

Air leaks as you mentioned. Filter head primer is often a culprit.

No experience with fuel cut solenoid failing myself, but this is worth looking at too.

Thanks for the tips, today I pulled the gauze filter and spring out but no change, after which I pumped the primer up quite hard which I never needed to do in the past and created a diesel puddle on the garage floor.

I guess first things first so I rang around to find a rebuilder to get it resealed if that is all it needs, after I refit it and if the problem persists it I should have a more solid starting place.

Must be a lot of different symptoms affecting diesel engines given I still have not seen anyone speak of the particular one mine has.

Thanks again.

 

[rgren2]

created a diesel puddle on the garage floor.

This does not sound normal. Where did the diesel spill from. A slightly perished hose allowing ingestion of air.

 

[GQ bush man]

Check oring on bottom of fuel filter (water in fuel sensor)often leaks from little tap that you can open..

 

[fnqcairns]

This does not sound normal. Where did the diesel spill from. A slightly perished hose allowing ingestion of air.

Sorry that was vague, it leaked from the pump proper..seemed to come from higher up on it as best I could tell.

 

[fnqcairns]

Check oring on bottom of fuel filter (water in fuel sensor)often leaks from little tap that you can open..

I still have the old original setup packed away, the car runs a Delphi cav unit, which might be a mistake now because I cannot find them anywhere here on the net for sale, let alone an original primer for it. The unit does not leak fuel at least.

 

[fnqcairns]

Today I am going shopping for a 17mm pipe wrench, some stumpy wrenches and I have the timing tool and gauge on order from ebay....will be dumping 3 month old radiator fluid out too so need more of that. Timing gear cover gasket if I can source one here. I think thats all the extra bits needed for this job.

 

[peterc3004]

Just a left of centre suggestion: is your fuel ok? No water or contaminates?

 

[NWGQ]

My ute has done the stalling thing at low revs for quite some time now. It will slowly start to die at idle until rev'ed up, it will hold for a little but then begin to die again.
One way to prove everything downstream of your pump is working fine is to wait until it starts to stall, then prime up with the hand pump. Initially it will be soft but then go solid as the revs pick up to normal idle speed again.

Easy things to check are the rubber connections to your filter and to your pump. I replaced all of mine and got nice hose clamps for them all, with no difference made. Because a GQ doesn't have a stand alone lift pump, it will suffer if the mechanical pump internals are worn out, I believe this is my problem. Yours could be a similar thing that has come on a bit more suddenly. I have a spare injection pump now so I'm not too worried, but previously I was thinking to put in an electric lift pump to ensure it had a steady supply.

 

[GQshayne]

The primer does fail over time. My recollection is that the CAV296 filter is simply an adapter which fits the standard primer head. So you should be able to get a new primer and then swap them over. Berrima Diesel may be able to help you with the CAV adaption if you cannot find anywhere local.

 

[fnqcairns]

Just a left of centre suggestion: is your fuel ok? No water or contaminates?

Lol funny you should say that, although the earliest most minor symptoms arrived before this but to save a 5-minute detour we have been filling up on the way home from camping these last couple times at a different but same brand servo so who knows! The glass bowl held no water though but otherwise I guess I will see when I fit the refurbished pump. The saving grace is that it is leaking so i have no choice but to spend the time and money but it will give a known good starting place to diagnose from further. Will keep the contamination in mind cheers.

 

[fnqcairns]

My ute has done the stalling thing at low revs for quite some time now. It will slowly start to die at idle until rev'ed up, it will hold for a little but then begin to die again.
One way to prove everything downstream of your pump is working fine is to wait until it starts to stall, then prime up with the hand pump. Initially it will be soft but then go solid as the revs pick up to normal idle speed again.

Easy things to check are the rubber connections to your filter and to your pump. I replaced all of mine and got nice hose clamps for them all, with no difference made. Because a GQ doesn't have a stand alone lift pump, it will suffer if the mechanical pump internals are worn out, I believe this is my problem. Yours could be a similar thing that has come on a bit more suddenly. I have a spare injection pump now so I'm not too worried, but previously I was thinking to put in an electric lift pump to ensure it had a steady supply.

A lift pump was one of the first things I was going to fit many years ago but never did, I hope yours holds out longer than mine, great to have a spare ready to go.

 

[fnqcairns]

The primer does fail over time. My recollection is that the CAV296 filter is simply an adapter which fits the standard primer head. So you should be able to get a new primer and then swap them over. Berrima Diesel may be able to help you with the CAV adaption if you cannot find anywhere local.

Ok good info thanks I will look into that the unit is the Delphi ad-7018/1a and at the time I thought it would remain common so was a good choice but times have moved on it seems..will look into the idea of an adapter setup, makes sense.

 

[peterc3004]

CAV filters were common on old tractors with the glass bowl on Perkins diesels etc

 

[fnqcairns]

Update:

After waiting for a nice puller to arrive in the mail then procrastinating for a few more days today I got stuck into it

This pump according to service history was replaced by Nissan at 70K km and the red rtv used I guess proves it, also the pump gear nut was only nipped up, all that kept it in place (I think) was the spring washer tang had worn into the nut creating a vertical wall...previous owners go lucky over the100K km travelled after.

Also, all bolts including the injector line nuts were at various levels of tightness, will do a better job than that this time.

Got me thinking does anyone have a recommendation for a good honest and careful pump re-builder in the cairn's region?..I have no idea so any comment welcome...this old girl I hope to keep until my licence get taken away in old age or at least for as long as possible.

cheers

 

[grumpyone]

Hi all this has me stumped but diesel engine diagnosis almost always does, I have read almost every injection related post on here without finding the same symptom explained.

For a while now (a few hundred km) I thought the GQ had a slightly out of balance front wheel/s, then last w/e when loaded up to go camping these unbalanced wheels got worse, then on the way home from the 300km round trip it felt like all 4 wheels were out of balance noticeably shaking us at highway speeds.

On way home after 100km at highway speeds we pulled into the sevo to fill up to find the problem had got worse over that portion of the trip now with noticeable surging/hunting at all throttle levels so the full tank made no difference, while out camping we did about 16 or so km of low range driving to get in and out without noticing the problem.

The surging is super quick at speed so feels like unbalanced tyres, when going slow around town it remains a constant on-off a couple time a second say but always accelerates through all while surging softly no matter the throttle setting.

After the trip I changed the CAV style filter but this made no difference, car is now idling lower as well threatening to stall so I am using the hand throttle to keep it running when idling, it seems to idle fine then.

Today going to check the gauze filter because I know I have one but after this I am stumped, an air problem is about my only real go to under the bonnet so ..what next?

Have checked out the cost of new injectors but the old girl up until this problem blew next to no smoke, started on a dime etc

First drivability problem in 16 or something years of ownership..knew this day would eventually come

This does seem to be fuel starvation,have you checked the in-tank pickup for shyte adhering to the screen ?

 

[fnqcairns]

This does seem to be fuel starvation,have you checked the in-tank pickup for shyte adhering to the screen ?

No, I did not even consider it actually, the pump leaks so when I get it back and if it still plays up (hope not) I will make it one of my first troubleshooting locations..cheers.

Will update here what the recondition-er thinks might have been the problem if he finds something.

 

[fnqcairns]

Update, fitted my rebuilt pump, doesn't leak anymore, car idles exceptionally well though and is super quiet, diesel guy said the suction side was clean ( I think this was in reference to my surging problem..dunno) got some moving parts replaced on the pressure distributing side.

I looked everywhere on this forum for the timing/plunger spec (.0.74mm)..given the manual but my official Nissan workshop manual doesn't show the vacuum pump in the right spot so the removal and refitting instructions are wrong I wanted backup.

Also, if you wanted to time by ear after the first start one of the mounting bolts is impossible to get at without a special or purpose made tool so getting it right the first time is important.

If I went by the marks I put on it, the timing was at .68 so glad I decided to do the job properly...the dealer Nissan mechanic who was here before me just guessed it seems..near enough is good enough.....a D- esp with forgetting to torque up the gear nut.

With reference to the great help gotten her the next job is to replace the hand primer, then if that fails get some clear plastic tube to replace the connecting fuel lines to look for air and the last thing before turning up at the mechanics is to inspect the in tank gauze filter...this is last because I will need to pull the camping setup out first.

cheers

 

[fnqcairns]

Still surging but much reduced like in the earlier stages. I added 2 stroke to the fuel just in case it is bad and therefore has a low lubrication value, purged the in tank filter.

I am now back to my original place of the injectors, i was wondering if 2 stroke has any lubrication effect on a bad injector?

Say if it is only spraying half or the like volume of fuel per opening as this could cause the rhythmic surge and the lubrication improved its function but not totally?

Going to look into a new set because it's time and will see how that goes.

Car is drivable again with the surging only constantly annoying.