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As promised, a how to guide on how to diagnose a replace the over pressure relief valve on an 2006 2.2 I-CTDi engine. My thanks goes to Jon_G for his advice on the diagnosis and valve replacement. You follow this guide at your own risk. If you're not confident then please appoint a garage. Where I use the phrase bolt/valve I mean the over pressure relief valve.

Symptoms;

Hard starting when the engine has warmed through and is encountered in the early days of the fault, possibly first noticed when the engine has had to be restarted soon after a journey. In the early days of the fault the car starts fine when stone cold and if immediately switched off it restarts again, this can be done several times and is okay. It's only when the engine has been warmed through that the hard engine starting trouble emerges. The longer the engine has been left from last use the engine will fire up more easily; after 15mins-30mins engine will not start, struggles to fire up after 1hr, more easily after 2hrs. Apparently this may have something to do with the viscosity of the diesel when warm as it is then more likely to leak past the faulty relief valve.

I noticed just before I changed the valve that the problem was beginning to happen with the engine from cold.

No symptoms encountered when driving, just don't stall that diesel engine!

Tools for diagnosis; pilers, pvc tubing, a container, adhesive tape and rags.

Look at the engine. The fuel rail is the tube with several brass nuts with narrow metal tubes (fuel lines) attached. To the left hand end of the tube, easily missed, is what appears to be a 17mm bolt. Close by is a black braided flexible tubing (low pressure fuel return pipe).

With the engine off, disconnect/pull off the black braided hose, you may need a flat bladed screwdriver to get this started. Attach PVC tubing to the end of the braided tube, seal with adhesive tape, put other end of PVC tubing into container. A 1pt milk bottle seemed to rest quite neatly in the engine bay. Place rages under the tubing and the now exposed metal tube.

Turn over the engine for about 10-15seconds. Return to the engine bay and inspect the container. If diesel is present either in the tube or in the container the over pressure relief valve is most likely to be faulty. See photo.



Congratulations, you may now decide if you want to replace the over pressure relief valve yourself or give the work to a local garage to do. The single most important consideration for a DIYer is being able to undoing that 17mm bolt/valve. It is seriously tight.

This is the bolt/valve



To get the bolt/valve off I used a 1/2" 75cm breaker bar and 17mm socket. The bar was placed on the crook of my right shoulder, my left hand was supporting the 17mm socket to keep this as true as possible on the bolt to avoid round the hex bolt corners. I then lifted using my leg muscles. The engine rolls about a bit when you lift. I nearly gave up but on the final attempt the bolt broke (loud bang). I checked the fuel rail mountings as I was worried these had snapped the base of the threaded mounting studs through leverage action while undoing the bolt/valve.

The valve is a Bosch part at ~£150. Note the fuel rail number eg xxx-RGB-xxxxx. A common number on the part found on the old and new valve was F166. On the part receipt it was called a "pressure limiting valve" p/n F00R001166. Use this information at your own risk.

Unscrew the bolt/valve but before complete removal place something that will guide the diesel from inside the fuel rail into a container. I used foil tape to force the flow/drip into a waiting empty sardine tray which proved satisfactory. If you don't use the tape to direct the flow the diesel will spill over the engine. Initially I was concerned that on removal the bolt/valve would be under positive pressure but figuring the over pressure valve was leaking the pressure would have dissipated enough. I wore safety glasses just in case of a squirt or splash.



I compared the new and old part and these were no obvious differences of the old compared to the new. I also marked the new bolt/valve so I knew roughly how far I had to tighten the bolt/valve. This was done my matching the thread.



To the left, old over pressure relief valve, you can see the extent of the forces applied in some rounding of the hex bolt corners.

Install the new over pressure relief valve making sure the new o-ring (supplied) is installed. I did not used thread lock. Initially I tightened this up by hand, then gently turned using a ratchet until it could go no furhter, then with the breaker bar turned approximately 1/16th to 1/8th of a turn which was where the new marking on the bolt/valve lined up with the original yellow temper/movement mark on the fuel rail. I used my torque meter after tightening but all I can say is that it was over 80Nm which was the upper limit of my 3/8" torque metre. It needs to be tight due to the pressures inside the fuel rail. I understand the bolt/valve has to withstand pressures reaching 1600psi, if the bolt/valve is loose it will fly out like a bullet.



Job nearly done. At this point you can choose to fire up the engine or you can bleed the fuel lines at the fuel injectors.

I decided to bleed the fuel lines. For this you need to disconnect the electronics to each injector to allow the spanner greater access to turn the nuts as otherwise this can be very tricky. I then wrapped rags around the nuts, reconnected the electronics to the injectors and turned the engine over for a short while and then stopped. After removing the rags you can see the diesel weeping. Tighten up the nuts to the fuel line to the injector. Wipe up excess diesel, if any.



Car should now start, maybe taking longer than usual as there could still be a little air in the fuel lines.

Idle for a few minutes. Check the bolt/valve marking for any bolt movement. Take for a test drive until the engine is thoroughly warmed through and return home. Recheck bolt/valve for any bolt movement, switch off.

Engine should restart with no hesitation :cool:

The job shouldn't take you long.
Undoing that bolt is the hardest part and possibly the only thing that could defeat the DIYer.

Hope people find this useful.
 

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Discussion Starter #2 (Edited)
Links to photos

View of over pressure relief valve test set up. Valve failed when diesel found in PVC tube and container.




View of over pressure relief valve to end of fuel rail. It's a 17mm bolt with yellow paint. Slightly askew as I'd already broken the bolt/valve.




Over pressure relief valve removed. Note foil tape to force drip away from engine into sardine tin.




Matching the threads, old (left), new (right), marked with a line so I know how far to tighten bolt/valve to match old yellow paint on fuel rail body. Note damage to corners of Hex bolt when valve was undone.




Weeping fuel lines to diesel injectors after bleeding.




Over pressure relief valve after ~1k miles. No bolt/valve movement seen.



No problems to report to date.
 

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Hi DP, would you mind if I put a link to this thread on TypeAccord... I've helped a few members there with this exact same problem and this write-up would make a nice reference there as well as here.
Jon.
 

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Hi Jon_G,

No problem. Share the knowledge.

I asked for help, it's why I joined this forum, this is my way of giving back.

Dom
 

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Thank you!

I have this problem exactly. The EML came on as it got to the stage where it wouldn't start cold either. New battery, new glow plugs - no improvement (plugs had done 120,000 miles and battery was 4 years old). Took it too coal garage who couldn't diagnosed the fault so took it to Brayley Honda in Enfield. They diagnosed a glow plug ECU fault and replaced glow plugs (again as they said 2 had failed…) and put in a new ECU. All for under £500 which I didnt think was too bad. It now starts cold but not warm or hot. Had the RAC out to me to squirt in some easy start which got it going. Therefore must be a fuel fault.

Been back to Honda Brayley again - they have no idea and suggest complete replacement of the fuel rail and system as a meagre cost of £2-2.5k. With 130k on the clock I don't really fancy that so will try this. Once started it runs well, if a little underpowered.

Any idea if it could be anything else before I replace the relief valve?

Thanks
 

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I have this problem exactly. The EML came on as it got to the stage where it wouldn't start cold either. New battery, new glow plugs - no improvement (plugs had done 120,000 miles and battery was 4 years old). Took it too coal garage who couldn't diagnosed the fault so took it to Brayley Honda in Enfield. They diagnosed a glow plug ECU fault and replaced glow plugs (again as they said 2 had failed…) and put in a new ECU. All for under £500 which I didnt think was too bad. It now starts cold but not warm or hot. Had the RAC out to me to squirt in some easy start which got it going. Therefore must be a fuel fault.

Been back to Honda Brayley again - they have no idea and suggest complete replacement of the fuel rail and system as a meagre cost of £2-2.5k. With 130k on the clock I don't really fancy that so will try this. Once started it runs well, if a little underpowered.

Any idea if it could be anything else before I replace the relief valve?

Thanks
It is very disappointing that a Honda dealer has failed to properly diagnose your problem. But, as you say, if it starts with easi-start then it must be a fuel issue.

There are two common reasons why the fuel rail fails to pressurise during starting, the fuel rail pressure relief valve leaking (as brilliantly described above) and the fuel injectors developing excessive leak-back, where the built-in lubrication path through the injectors (which then flows back to the fuel tank) becomes much, much greater on one or more of the injectors to the extent that practically all fuel pressure generated during starting goes back to the tank. This is often worse when hot to begin with, as the warmer diesel flows at a quicker rate through the injectors.

I'm assuming that you've not yet checked the fuel rail pressure relief valve for leakage, as described above? You really should! Don't let a garage fit any new parts without proof that either this valve or the injectors really are at fault, as all these tests are easy DIY tasks. Injector leak-back tests can be found on YouTube and basically consist of removing the lines back to the fuel tank and fitting plastic tubes to the injector outlets, running these tubes to clear plastic containers and then watching how much fuel comes out while the engine is cranked over (or allowed to idle)... injector(s) that flow much higher amounts than the minimum one need to be replaced (which can be tricky). I'd check the valve for leakage first, as it's really easy to do this check, and really cheap and simple to fix.
 

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Brilliant advice

Ok that is amazingly helpful. There is more helpful information here than provided by Honda which is slightly sad really. I am grateful to you for taking the time to reply. I adore my car and want to keep it going!

I haven't yet check the relief valve as I had asked Honda to check the fuel system. They have just said they recommend replacing the whole rail which sounds like a typical main dealer response of we can't be bothered.

I will check the valve tomorrow and then the injectors as you suggest. I will post a response once I've done that and let you know which one it was (hopefully it will give a diagnosis!).
 

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Ok that is amazingly helpful. There is more helpful information here than provided by Honda which is slightly sad really. I am grateful to you for taking the time to reply. I adore my car and want to keep it going!

I haven't yet check the relief valve as I had asked Honda to check the fuel system. They have just said they recommend replacing the whole rail which sounds like a typical main dealer response of we can't be bothered.

I will check the valve tomorrow and then the injectors as you suggest. I will post a response once I've done that and let you know which one it was (hopefully it will give a diagnosis!).
Honda will only sell you the complete fuel rail as they do not hold the individual items that attach to it (e.g. the pressure relief valve and the pressure sensor) BUT Bosch (who supply these parts to Honda) do sell them through their service centres... DeltaPapa bought his valve this way. Or you can buy a secondhand fuel rail from a breakers, which is what I did.

Good luck, I hope it's the valve not the injectors.

Here's a Honda diagram (albeit for my slightly older Accord) showing the fuel rail as part #1 and the pipe you need to remove to check for leakage as part #3... http://www.lingshondaparts.com/honda_car_parts_selection.php?block_01=17SED01&block_02=E__3320&block_03=608 Look at those (ex. VAT) prices and weep! The valve is the thing installed at the lefthand (furthest) side of the rail and is not listed as a separately available part.
 

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It's the valve - phew!

Checked everything this morning. Started by checking I could overcome the thread lock on the valve which I could do quite easily with a standard breaker bar. Had my home-made scaffold pole extension to the breaker bar handy but didn't need it.

Checked the valve and it is sending fuel back to the tank. I had also spoken to the 'technician' at Honda yesterday and asked them to check the valve and the injectors - they also said injectors were fine and valve was faulty - permanently open.

There is a diesel part specialist in Ipswich:
A.P. and E.M. Hewing

Evelyn Hewing
31
Roundwood Road
Ipswich
Suffolk
IP44LU
United Kingdom

Phone:07703903751
Email:[email protected]

who can order the part for £102 plus £4 P&P plus VAT for a Bosch one, not a copy so will do that tomorrow morning. I'm hoping that will be the end of it.

I'll let you know!

BTW - I'm still running on the original wheel bearings and clutch at 130,000mi. Anyone know if and when they have replaced theirs?

Al
 

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Checked everything this morning. Started by checking I could overcome the thread lock on the valve which I could do quite easily with a standard breaker bar. Had my home-made scaffold pole extension to the breaker bar handy but didn't need it.

Checked the valve and it is sending fuel back to the tank. I had also spoken to the 'technician' at Honda yesterday and asked them to check the valve and the injectors - they also said injectors were fine and valve was faulty - permanently open.

There is a diesel part specialist in Ipswich:
A.P. and E.M. Hewing

Evelyn Hewing
31
Roundwood Road
Ipswich
Suffolk
IP44LU
United Kingdom

Phone:07703903751
Email:[email protected]

who can order the part for £102 plus £4 P&P plus VAT for a Bosch one, not a copy so will do that tomorrow morning. I'm hoping that will be the end of it.

I'll let you know!

BTW - I'm still running on the original wheel bearings and clutch at 130,000mi. Anyone know if and when they have replaced theirs?

Al
Great news. Glad it was the easy and relatively cheap fix.

So you ended up telling a Honda tech how to test for this problem? That doesn't look good, does it?
 

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Great news. Glad it was the easy and relatively cheap fix.

So you ended up telling a Honda tech how to test for this problem? That doesn't look good, does it?
Well, I asked then to specifically test the valve and the injectors. Prior to this they has said they thought it was a fuel system problem but there was no way of checking the individual components and even if the fuel rail was replaced they couldn't guarantee the car would work. After checking the valve and injectors, by some miracle they were able to tell me "yeah, well we're 99% positive that the valve has failed as its permanently open so if its replaced then that should fix it". Amazing how there was no way of checking the components, until I told them about Civinfo and how I had been discussing this common problem with fellow forum users, and would they like me to tell them how to test the individual components of the fuel system?
 

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Checked everything this morning. Started by checking I could overcome the thread lock on the valve which I could do quite easily with a standard breaker bar. Had my home-made scaffold pole extension to the breaker bar handy but didn't need it.

Checked the valve and it is sending fuel back to the tank. I had also spoken to the 'technician' at Honda yesterday and asked them to check the valve and the injectors - they also said injectors were fine and valve was faulty - permanently open.

There is a diesel part specialist in Ipswich:
A.P. and E.M. Hewing

Evelyn Hewing
31
Roundwood Road
Ipswich
Suffolk
IP44LU
United Kingdom

Phone:07703903751
Email:[email protected]

who can order the part for £102 plus £4 P&P plus VAT for a Bosch one, not a copy so will do that tomorrow morning. I'm hoping that will be the end of it.

I'll let you know!

BTW - I'm still running on the original wheel bearings and clutch at 130,000mi. Anyone know if and when they have replaced theirs?

Al
I have now replaced the hydraulic fuel over-pressure valve and this has cured the problem completely. Viva la Civinfo! Cost was £130 delivered from Andy Hewing. Enfield Auto Spares also can source this part for £89 but don't deliver. Notably - my fuel economy has improved by 25% to 55mpg which is what I used to get until about 4 months ago when this all started and it declined to 44mpg.

Thanks to everyone for helping me beat the system on this one.
 

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HI ALL , new to the site, i have a 57 plate 2.2 CDTI, And i think i might have the same problem? engine today took an age to start , (cut out twice! ) and was running really lumpy. (wife was driving the car). took the car out myself , gave it a good 'HARD ' ;) DRIVE and this seemed to sort the problem for the moment . had the car serviced , and fuel filter changed etc 2 weeks ago, nad have done approx 800 miles since. the question is should this be my next load of checks ? any assistance would be gratefully recieved.
 

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I's expect it to run OK, once started, if the valve (or an injector) was leaking excessively back to the tank.

What fuel filter was fitted recently? Was the car OK before this? Your car should only ever be fitted with a Honda filter (actually made by Denso).

Any warning lights? I guess you would have mentioned this!

Welcome to Civinfo!
 

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Hi again , your correct yesterday there were no fault codes , but this morning we have PGM -F1 come up ,and it wont rev over 2000 ?
really stumped ?:facepalm:
 

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not sure what filter was fitted , had a mechanic i trust , do the service etc, and he 's been in an accident , and i cant speak to him.
It won't go over 2k rpm as it's in 'limp mode' because the ECU has detected the problem and there should now be a Diagnostic Trouble Code (DTC) stored in the ECU, this could be read using an OBD2 reader... do you know someone who has one and could read the DTC for you?

He may be a trustworthy mechanic, but he may not have realised how sensitive this engine is to having the correct fuel filter!

Did this problem only happen after the car was serviced?
 

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Hi jon , many thanks for your help , yes, i do have a mate with an OBD 2 reader who will check it tommorrow , and yes, it was playing up a bit before the service , (but not to this extent) but since it had run well for 2 weeks , i am confused and thought it best to ask the experts. once again many thanks for your help. would a pattern filter make this problem occur ? if so think that might be the first port of call , what do you think?
 

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Hi jon , many thanks for your help , yes, i do have a mate with an OBD 2 reader who will check it tommorrow , and yes, it was playing up a bit before the service , (but not to this extent) but since it had run well for 2 weeks , i am confused and thought it best to ask the experts. once again many thanks for your help. would a pattern filter make this problem occur ? if so think that might be the first port of call , what do you think?
Never use a pattern/aftermarket fuel filter on these engines... this forum and TypeAccord are both littered with threads where cars have played up after having a non-OEM filter fitted.

DTCs P1065 and/or P0087 are both signs of needing to have the fuel filter replaced.
 

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Hi Jon/all,
on the way into work this morning , the engine management light went out !!! still did the scan and the OBD 2 reader came up with p1066 , fuel rail preasure higher than expected , and P1086,fuel rail preasure(frp) regulator malfunction. HELP !! lol should i still replace the filter again , as i am not sure if it is a genuine part , or would it be best to replace something else ?
 
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