Rover P5B Fuel Filter Safety. There was an interesting and valuable discussion on the Rover P5 Club Forum regarding fuel filters for the P5B, started by another Richard (not me). Richard was highlighting potential safety concerns with the design of some widely-available aftermarket fuel filters for the Rover P5B that look similar to the original item, but differ in an important area.
As sometimes happens, the P5 Club took a dim view of discussion of anything club-related on the forum rather than it being raised to the club. Unfortunately the thread is no longer available.
I thought Richard had raised an important concern, so I decided to do some investigation. If you own a P5B or a car using a similar plastic in-line fuel filter arrangement I urge you to continue reading. And if anyone wants to comment on this article, please feel free to do so.
I should say that I have no experience of problems with any of these filters – I’ve always used filters from J.R. Wadhams – but there are some interesting differences between seemingly similar designs that everyone should be aware of.
It’s also worth saying that even the best filters need to be fitted correctly and checked for leaks. The potential for fuel leaks and a resultant fire needs to be taken very seriously.
Before We Begin: Fuel Lines
When I bought my car in 2015 it still had its original factory fuel lines, which were thin-wall plastic pipe very different to modern versions. This is now around 50 years old, and was never intended for use with todays fuels that contain ethanol and other additives that can degrade fuel lines. I recommend replacing all fuel lines with good quality modern versions that are rated for modern fuels (with their Ethanol content which can degrade older hose and seals not designed to be resistant).
The P5B Fuel Filter
The P5B uses an inline fuel filter, originally made by A.C. Delco, positioned between the fuel pump and carburettors. The filter is mounted next to the cylinder head on the left front of the engine. The filter is made of plastic, but rather than the hose being clamped directly to the ends of the filter, the factory used compression fittings with a copper ‘olive’, much like household plumbing compression joints. The compression fittings are an interference fit on the pipe, and when they are tightened the olive deforms and clamps against the plastic ’tails’ of the filter and the walls of the fitting, creating a seal with the fuel pipe.
This has always struck me as somewhat odd, as the filter is plastic so it can deform and bend, which isn’t ideal for a compression fitting. The copper olive and plastic filter can’t ‘adjust’ to each other as they flex in the same way a hose can do.
As noted on Wikipedia, “Compression fittings…are typically used in applications where the fitting will not be disturbed and not subjected to flexing or bending….Compression fittings are much more sensitive to these type of dynamic stresses.” You can read the full article here: https://en.wikipedia.org/wiki/Compression_fitting
Many experienced owners seem satisfied that this works well, and I am not doubting that it works if everything is as the factory specified. I’m sure if Rover became aware of a serious problem they would have changed the design. Yet it seems an odd design decision as you still have the issue of sealing the hose onto the compression fitting, so it doesn’t remove that failure point. All it achieves is adding 6 more components (the olive, and the male and female compression fittings at each end) and two extra potential failure points (the compression seal). Maybe I’m missing something.
However, I do believe issues may arise when non-original or aftermarket filters are used – this is the issue Richard was highlighting, and I’d like to discuss that here.
So Whats the Issue?
The issue is that some aftermarket filters do not have sufficient length at their ends for the olive to clamp correctly. The concern is that this could allow fuel to leak from around the joint, with all the potential problems that poses. This is made more serious by the previously mentioned engine vibration and the location of the filter on the P5B, above and forwards of the left-hand exhaust manifold.
It’s interesting how Wikipedia notes the sensitivity to dynamic stresses – the fuel filter on a P5B is clamped to the left-hand cylinder head, so is subject to all of the vibrations of the engine. This is made even worse if the owner has fitted an electric fuel pump, as then one end of the fuel pipe is likely to be secured to the fuel pump on the inner wing, whereas the other end of the pipe that attaches to the filter is moving with the engine. Even if the original fuel pump is used (which is obviously bolted to the engine so moves with it) the whole pipe > filter > pipe assembly will be moving and vibrating with the engine.
Whats more of an issue is that compression fittings seal by deformation of the ‘olive’ or ferrule around a pipe (the pipe being the tail ends of the fuel filter in our situation). Wikipedia explains better than I can: “When the nut is tightened, the ferrule is compressed between the nut and the receiving fitting; the ends of the ferrule are clamped around the pipe, and the middle of the ferrule bows away from the pipe, making the ferrule effectively thicker. The result is that the ferrule seals the space between the pipe, nut, and receiving fitting, thereby forming a tight joint.”
Here’s a section diagram showing the situation for the P5B fuel filter, with a correctly fitting filter:
Rover P5B Fuel Filter Hose Fitting.
The fuel filter is on the left of the diagram. The olive is shown in orange, and the orange arrows show the compression forces applied to the olive, which deforms when the angled faces of the fittings are screwed together. It’s important to note that the only purpose of the thread is to apply a compression force to deform the olive – the thread isn’t part of the seal.
In the diagram the compression forces cause the olive to deform both against the fittings and the ’tail’ of the filter. The deformation is most critical at point ‘A’ on the diagram, as that prevents fluid leaking out to the threads (which aren’t part of the seal). This is where there may be a problem with some P5B fuel filters – if the filter tail isn’t long enough, then the olive might not seal at point ‘A’. Combine that with flexing and vibration, and there is a real possibility that the joint will leak.
Is There a Problem?
In order to understand what’s available for purchase and how they compare, I bought 4 brand-new filters from different sources:
- J.R. Wadhams. Fuel Filter: V8. Brand: Coopers Fiaam Filters. Price: £24.00 plus postage.
- eBay / Roverpart of London. Fuel Filter Replacement 606168. Price: £16.95 plus postage.
- eBay. NOS Fuel Filter 606168 Rover. A.C. Delco / Delphi. Price £35.00 including postage.
- Rover P5 Club. P5B Fuel Filter. Price £7.00 including postage.
These were all bought and paid-for, not provided as ‘samples’, so I can be completely fair and honest in my opinions.
Here’s how they look:
Rover P5B Fuel Filter Group Comparison.
At a distance they all look similar, and the threaded fittings all fit the hoses in the P5B, so they should be OK, right? Well, no.
Lets take a closer look at each one to see why.
1. J.R. Wadhams
J.R. Wadhams Rover P5B Fuel Filter.
Here’s the J.R. Wadhams filter – this comes with the olives and compression fittings already fitted. This is a branded Coopers Fiaam filter, and the olives are fitted well-back from the end of the pipe, as they should be. This allows the olive to compress against the filter tail as per the original and the diagram above. Here’s a close-up of the olive:
The length of the ‘tail’ on each end of the filter is 16mm. This is where the olive and compression fitting sit, and 16mm allows plenty of room for the olive to fully and correctly seal against the filter, with a very healthy safety margin. This is also within 1mm of the A.C. Delco / Delphi item. These filters are a made in the EU and seem very well made, so I’d rate them as good value overall.
Overall Rating: 90%
2. eBay / Roverpart
eBay / Roverpart Rover P5B Fuel Filter.
Superficially this item looks similar to the others, but lets look more closely at the ends. As you can see, the ’tail’ at each end of the filter is actually very different. On this filter the tail is stepped at the filter body, so that the actual usable length of tail that the olive has to seal against is too short. Lets look more closely:
As you can see, in fact the end of the olive actually overhangs the end of the filter tail, so canlt seal against it when compressed. Due to the step, the usable ’tail’ on this filter is only 6mm long. That’s a full 11mm shorter than the original. You may be lucky and find it won’t leak, but the seal may either fail to form correctly when compressed, or will be much weaker than the original in service.
Here’s a modified version of the section diagram showing a representation of this filter, the ’step’, and how that may cause the critical part of the olive seal (point ‘A’) to fail:
The fact that the end of the olive sits beyond the tail of the filter makes this a very poor design, and one that I believe to be unsafe. I won’t be fitting this item to my car. Combined with the price, this is an extremely poor value item.
Just to be clear, after seeing this issue I checked to make sure the olive was pushed-on as far as possible and this wasn’t just an assembly issue at the factory. It wasn’t – the step prevents the olive going any further onto the tail.
Overall Rating: 0%
3. eBay: A.C. Delco / Delphi
eBay: A.C. Delco / Delphi Rover P5B Fuel Filter.
This is sold as a New Old Stock (N.O.S.) item. I have no way of verifying that – it’s supplied in an unbranded box, but it has ‘MADE IN ENGLAND’ moulded in one end of the filter body, and comes with an instruction sheet. As far as I can tell this is an original A.C. Delco / Delphi item, as the eBay seller claims.
I can see no issues with this filter. The usable tail length is 17mm, which is plenty of space for the compression joint to seal correctly, and it seems very well made.
As you can see, the filter is supplied with the olive and compression fitting separate. Here is the filter with these fitted:
The only downside of this item is the price, but then it is N.O.S. and Made in England. That means there’s only a finite number of these remaining. Here’s the instruction sheet that comes with it:
Overall Rating: 80%
4. Rover P5 Club
Rover P5 Club Rover P5B Fuel Filter.
This filter is only available to club members, and can be ordered through the club magazine. It is somewhat similar to the eBay/Roverpart item above in that it has a stepped ‘tail’, but with the important difference that the tail is somewhat longer – in this case the usable tail length is 10mm.
This is on the limit of what I believe to be acceptable, leaving no margin for error in how the olive seals – the end of the olive sits about 1-2mm from the end of the tail. It is not as bad as the eBay/Roverpart item, but it’s certainly not as good as the J.R. Wadhams and A.C. Delco / Delphi items in this important respect.
This item is very reasonably priced.
This filter comes with two clamps in the box, shown in the photos. I assume these are hose clamps if you don’t want to use the factory compression joint. However, they’re unlike any hose clamps I’ve ever seen, as they don’t wrap all the way around the hose, potentially leaving a section of unclamped hose. If anyone can confirm what these are for, please leave a comment.
Overall Rating: 50%
You can see for yourselves in the close-up photos that these filters differ quite markedly in the important area of the compression joint. They fall into three main groups. In the first group, I would rate the J. R. Wadhams filter as being the best considering price and suitability, with the N.O.S. A.C. Delco / Delphi item second due solely to the high price. You may value originality enough to place the A.C. Delco / Delphi item first, but I don’t think there will be much difference in their performance and safety.
In the second group, and in third-place overall I would place the Rover P5 Club filter. I judge this as marginal in how well the compression joint will work. I have no evidence that this has caused any problems in use, but there seems to be little margin for error in how well the olive seals. On the plus side, this item definitely has price on its side though – it is very reasonably priced.
Lastly, I rate the eBay/Roverpart item as unsafe, and recommend you don’t use this item. The compression joint will be severely compromised by the length of the tail, as one end of the olive has nothing to seal against. You’re relying on the olive being a snug fit on the tail, and the compression thread to form a seal. That really is the end of the story – even if this was being given away I wouldn’t use it. Yet it actually costs £16.95 plus postage (at the time of writing).
J.R. Wadhams Fuel Filter: 90%
eBay: A.C. Delco / Delphi Fuel Filter: 80%
Rover P5 Club Fuel Filter: 50%
eBay / Roverpart Fuel Filter: 0%
It’s worth mentioning that manufacturing tolerances may mean you see slightly different results, but that could work either way where the filter tail-length is marginally long enough – other examples may be better or may be worse.
So there you have it. An issue that was raised by Richard on the Rover P5 Club Forum highlighted what I think is an important issue that P5B owners (and perhaps owners of other cars using Rover V8 engine) need to be aware of.
If you have any thoughts or experience on this issue, please leave a comment below.