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Discussion Starter #1
Hi all.

It is back, a flat spot that comes and goes. It is when accelerating, it feels like the turbo has slowed boost and then it goes again. I have put in a new MAF sensor, cleaned the earth straps on the engine. It has a DTronic, but i put it in after the MAF was done. When i put the MAF in it seemed to be great, but now it is back. I was going to take it into Nissan and get them to look but each time they say no fault found. I am not sure if it is normal, but when i have left the car say over night, i can push the primer pump and pump it up about 6-8 times. I thought once it is primed it should stay hard. Me thinks it make have and air leak in the fuel systme causing the flat spot. The other though i have heard mention of the throttle position sensor been stuffed and sending the wrong throttle position to the ECU.

Any help would be great as it is giving me the ****s. It feels the Dtronic gain i had is not there anymore.

Cheers

Stuart
 

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Hi Stuart, as you mentioned, either you have air leaking into the fuel line or there is a problem with the primer pump.

The usual culprit is the O ring on the bottom of the fuel filter, this needs to have a good seal or air will get in. Tighten it with a lot of force (this can be done with all things connected with some multigrips) and try the push test again.

Cheers,
Whitie
 

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Stuart,

Have you blocked your EGR valve? Many people have said that the dreaded flat spot disappears after blocking the EGR. If your EGR valve sticks open under load, it could be the reason and if it frees itself after a while, the flat spot disappears. ZD30 EGR valves are known to be problematic, so even blocking it temporarily to see if it’s the problem may be worth doing.
You won’t get a code if the EGR valve sticks, because the ECU just wants to see the circuitry regardless if the valve is open or closed.

Whitie, my primer would always give a couple of pumps before firming up first thing in the morning. Even the electric pump rattles away for a couple of seconds when the glow plugs warm. Feeling for fuel under the filter should tell you if you have a leak.
 

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Discussion Starter #4
Thnx for the replys guys, I will have a look at the seal at the bottom of the fuel filter, however i just replaced the filter and new seal. Is there a way to check visually if the pirmer pump and the EGR are stuffed. Once i block the EGR will i have to do anything else...

Hope this is the fault. Are the primer pumps expensive and can you lubricate the EGR if it is sticking...

Thnx in advance

Stuart
 

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Discussion Starter #5
Chaz said:
Stuart,

Have you blocked your EGR valve? Many people have said that the dreaded flat spot disappears after blocking the EGR. If your EGR valve sticks open under load, it could be the reason and if it frees itself after a while, the flat spot disappears. ZD30 EGR valves are known to be problematic, so even blocking it temporarily to see if it’s the problem may be worth doing.
You won’t get a code if the EGR valve sticks, because the ECU just wants to see the circuitry regardless if the valve is open or closed.

Whitie, my primer would always give a couple of pumps before firming up first thing in the morning. Even the electric pump rattles away for a couple of seconds when the glow plugs warm. Feeling for fuel under the filter should tell you if you have a leak.
I can pump the primer about 6-8 times when left for a while. That said it does start up easy even when cold...
 

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stuartcarr2002 said:
I can pump the primer about 6-8 times when left for a while. That said it does start up easy even when cold...
you have an air leak in the fuel system. most likly fuel filter or primer pump (check o rings, just had someone on navara forum that had one of the o rings missing). it should go hard in 1-2 pumps no more.
these systems do not like air in the fuel one bit, fix asap.
 

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Remember GU Deano?

His diesel pump had a seal that leaked into the sump and fairly quickly thinned the oil and blew things up.

I'd be looking into where the air is getting in. Could be a simple fix, I'm hoping for you Stewie anyway.
 

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Discussion Starter #8
GU Deano, how could i forget :)

Can you pull the primer apart ???
 

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wasn't GUDeano the one where the seal on the injector return (spill) leaked. apparantly its a manafacturing fault.
 

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Chaz said:
Whitie, my primer would always give a couple of pumps before firming up first thing in the morning. Even the electric pump rattles away for a couple of seconds when the glow plugs warm. Feeling for fuel under the filter should tell you if you have a leak.
Hi Chaz, I'm not sure if that would be normal?

That was a tell tale sign for me that I had an air leak somewhere, once I fixed it, now the primer is firm in the morning - no give at all.

It is obviously not causing you any grief though so I wonder if it is worth getting to the bottom of?

Cheers mate
 

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a couple of pumps can just be from air mixed in the fuel by it sloshing around in the tank, especially on rough roads. however any more than 2 pumps i would suspect air leak. fit a bit of clear fuel hose and check for bubbles.

pump will always rattle for a bit first thing as it builds pressure.
 

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whitie said:
Hi Chaz, I'm not sure if that would be normal?

That was a tell tale sign for me that I had an air leak somewhere, once I fixed it, now the primer is firm in the morning - no give at all.

It is obviously not causing you any grief though so I wonder if it is worth getting to the bottom of?

Cheers mate
Hi whitie,

I haven’t started my car for 4 days, so I just went out and pumped the primer. It took 3 strokes of the pump before it was firm on the 4th stroke. As far back as I can remember it has always been pretty much the same. The system does hold pressure, but over time it should release it through the priming pump to the tank. Even the check ball in the electric pump wouldn’t seal off all that well.

Wouldn’t I have a fuel leak if there was pressure escaping outside the fuel system?
I would have thought that if there was air getting in, the primer wouldn’t firm up at all.

Thanks for the input mate, something to think about.
 

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Chaz said:
Hi whitie,

I haven’t started my car for 4 days, so I just went out and pumped the primer. It took 3 strokes of the pump before it was firm on the 4th stroke. As far back as I can remember it has always been pretty much the same. The system does hold pressure, but over time it should release it through the priming pump to the tank. Even the check ball in the electric pump wouldn’t seal off all that well.

Wouldn’t I have a fuel leak if there was pressure escaping outside the fuel system?
I would have thought that if there was air getting in, the primer wouldn’t firm up at all.

Thanks for the input mate, something to think about.
G'day Chaz, if it is only a small leak, the primer will firm up.

If all is sealed, the VP44 will hold vacuum to the fuel line so the primer should be firm / full with no air. It would make sense that if there was an air leak that there should also be a fuel leak as the line is now under pressure however it seems that it may be too small a leak to detect?

I am still not sure how much of a problem it may be in these circumstances if at all.

My primer was firm since the day I picked up the truck so I new that I had created a problem after I changed the fuel filter and it could be primed in the morning.

:cheers:
 

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whitie said:
G'day Chaz, if it is only a small leak, the primer will firm up.

If all is sealed, the VP44 will hold vacuum to the fuel line so the primer should be firm / full with no air. It would make sense that if there was an air leak that there should also be a fuel leak as the line is now under pressure however it seems that it may be too small a leak to detect?

I am still not sure how much of a problem it may be in these circumstances if at all.

My primer was firm since the day I picked up the truck so I new that I had created a problem after I changed the fuel filter and it could be primed in the morning.

:cheers:
Thanks whitie,

Could the problem just be the primer pump itself, letting pressure escape back to the tank? I'm just curious because I can't find a fuel leak anywhere.

Cheers mate.
 

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Discussion Starter #15
Hi all

I think maybe the same is hapennign with mine. I might just by the primer pump and see what happens as it takes about 6-8 pumps to get it hard (primer that is ) :)
I hope i wont get any damage to the fuel system caused by the air leak. The flat spot only happens when you are driving hard, soft driving it rarly happens. Does anyone know how much the primer pumps are through Mr Nissan. It is under warranty but it would be too hard to convince nissan that there is anything wrong with it...
 

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Chaz said:
Thanks whitie,

Could the problem just be the primer pump itself, letting pressure escape back to the tank? I'm just curious because I can't find a fuel leak anywhere.

Cheers mate.
Hi Chaz, yes it could be the primer pump. The only way that I can think of for finding the leak is to put a vacuum on the outlet of the filter - that fancy "T" piece that you installed would be a good place to connect to ;) - maybe to 10 or 15hg.

If it instantly loses the higher vacuum, then you may have a chance at finding the culprit. If not, I honestly would not worry about it as you have the lift pump to get things going again.

All the best mate.

stuartcarr2002 said:
Does anyone know how much the primer pumps are through Mr Nissan. It is under warranty but it would be too hard to convince nissan that there is anything wrong with it....
Hi Stuart, I would give Nizzbits a PM, I am sure that he would have a good price for you.

Cheers.
 

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stuartcarr2002 said:
Hi all

I think maybe the same is hapennign with mine. I might just by the primer pump and see what happens as it takes about 6-8 pumps to get it hard (primer that is ) :)
I hope i wont get any damage to the fuel system caused by the air leak. The flat spot only happens when you are driving hard, soft driving it rarly happens. Does anyone know how much the primer pumps are through Mr Nissan. It is under warranty but it would be too hard to convince nissan that there is anything wrong with it...
guys with navara have been having problems with motors cutting out due to air leaking into the fuel.

also with these types of leaks you don't neccarly get fuel leaking out.

primer seams to be common fault but concidering how many times it would get used i'm suprised so many seam to be failing.

easy way to find air leak is to fit clear fuel hose both sides of fuel filter, you will soon see air bubbles.

FIX ASAP ! ! !
 

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Discussion Starter #18
Well, up date.

I spoke to Nissan the other day about the flat spot and getting a price on the primer pump. he told me the price but also mentioned that there is an O ring that fits on the upper side of the fuel filter. Not the big one but a small thick ring that is the size of a 20cent piece. He told me that it is common for it to not get put back in when the filters are changed. It costs $1.50. I put it in last night, but havnt had a drive yet, as soon as i do i will keep the thread posted. Hopefully it fixes the problem. The spares guys said that a ZD30 that doesnt have this oring becomes a real dog.

For anyone with flat spots or air leaks in to the fuel system, maybe worth checking this oring if it is missing...

Cheers

Stuart
 

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stuartcarr2002 said:
Well, up date.

I spoke to Nissan the other day about the flat spot and getting a price on the primer pump. he told me the price but also mentioned that there is an O ring that fits on the upper side of the fuel filter. Not the big one but a small thick ring that is the size of a 20cent piece. He told me that it is common for it to not get put back in when the filters are changed. It costs $1.50. I put it in last night, but havnt had a drive yet, as soon as i do i will keep the thread posted. Hopefully it fixes the problem. The spares guys said that a ZD30 that doesnt have this oring becomes a real dog.

For anyone with flat spots or air leaks in to the fuel system, maybe worth checking this oring if it is missing...

Cheers

Stuart
Mmmm, very interesting. I thought I read something similar recently... where was it.... I remember now, it was on post 2 of this very thread :p :p :p

Goodonya Stuart, I hope that it has fixed the flat spot for you - it never occured to me that it may not have been installed.

Cheers,
Whitie
 

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Discussion Starter #20
whitie said:
Mmmm, very interesting. I thought I read something similar recently... where was it.... I remember now, it was on post 2 of this very thread :p :p :p

Goodonya Stuart, I hope that it has fixed the flat spot for you - it never occured to me that it may not have been installed.

Cheers,
Whitie

Not the Oring on the water sensor thingy, this O ring fits inside the primer housing around the tread where the filter sits on. I presumed in the earlier thread that you meant the water sensor thingy o ring. My mistake :(

Thnx once again whitie, you know these bloody ZD's well...
 
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