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Can dirty fuel block injectors?

This post reports such an occurence.

I would have thought it was impossible, due to filters upstream. There should be a filter (100 micron mesh on a Socata TB) in the fuel selector and there is another one on the fuel servo inlet.

What could obviously happen is a fuel flow blockage due to the filter(s) getting blocked, which amounts to the same result

Shoreham EGKA, United Kingdom

Does anyone use one of these Mr Funnel filters? The largest one allows 15usg/pm so shouldn’t slow down fuelling too much.

I often considered getting one, but never did.

EIKH Kilrush


referring to your incident: I understand you can’t be 100% sure which airport supplied the bad fuel, but 99%. Did you inform / approach them at all? If not, that would still be a significant danger. So, was there any aftermath?

Also, as Peter asked; why didn’t the stuff get caught by the fuel filter? Did you go into this?

Last Edited by boscomantico at 01 Jan 12:09
Mainz (EDFZ), Germany

Do you mean one of these, dublinpilot?

This one claims 15 litres per minute which would slow down fuelling a great deal. 15 USG/min is 4x better but still quite slow.

What is interesting is how it could trap water. Is it really possible to trap water with a simple filter?

Shoreham EGKA, United Kingdom

Sorry Peter. I forgot to include the link!


It’s one of those, but there are a number of different models. The largest promises 15 gallons per minute (I assume that’s USG, so 57 ltrs/pm). It could fill the Arrow’s tanks from totally empty to full in just over 3 minutes at that flow rate (183 ltr).

Here’s a link to an Amazon seller.

One thing that I find interesting is that they don’t require maintenance such as changing the filters.

EIKH Kilrush

I had a problem with clogged injectors on my Cardinal RG right after I bought it. Turned out the idiots that had maintained it before I bought it had crushed the fuel strainer when they re-installed it letting tiny bits of PR sealant to get into the injectors.

At any rate, to get to the injectors, the fuel filter/strainer needs to be compromised.

I followed Eugene’s problems and it was never conclusively determined how/when/where the sand got there.


I don’t think you will ever conclusively determine how sand got into the fuel system.

One uncomfortable thing is that you can’t rule out vandalism, unless your filler caps are locking. After all, fuel thefts are quite common on the GA scene, and anybody doing that knows the danger they are creating.

One of the tests I had done on the 100 micron fuel filter found a deposit, visible under a 40x microscope we have at work

which the lab thought was probably talcum powder. I had spent a few hundred quid on the electron microscope analysis and didn’t bother to test further, but talc is not supposed to be in the fuel either!

Shoreham EGKA, United Kingdom

Blocked injectors are not unknown, we had problems on an O-540, the engine had no EGT indication so we eventually found the problem cylinder using a laser thermometer.

Fuel contamination is most likely during maintainence, it is almost imposable to keep all the dirt out of system due to the very small particals that can give problems.

I sometimes think that these problems result from over maintenance, I can remember removing the filters from the Boeing 747 anti skid system modual for " cleaning ". This practice carried out in a dirty landing gear bay usualy resulted in defects that had not been present when the aircraft rolled into the hangar.

In short we need to decide if a filter is used to protect the unit or the filter is to protect the filter that protects the unit ? In my view the former should not be removed during normal maintenance and the latter should.

My engine issues coming back from Turkey in the spring turned out to have been caused by very small particles of sand in the fuel. Just like C210Flyer, I had several iterations where the problem was considered fixed only to have the issue again, until we did a full clean of the fuel system and of the tanks. Actually I stopped at Straubing too, and it was after C210Flyer’s issue, so I’m even more annoyed with them for resisting my call for a full clean – which would have saved me an emergency landing.


Sorry for being absent so long. Spent 1/2 the day clearing the snow and ice off the plane in Augsburg only to have it rain and pour the last hour. Well at least its clear of ice until the rain freezes on it. tomorrow night.

Ok back to business. The particles that were found felt gritty when rolled with thumb and finger. Some were a bit bigger than others but all in all it was very fine. Michael was right the fuel filter was crushed.But we only found this out at the second maintenance shop. So either it was crushed before Straubing which meant it would have been changed or accidentally crushed with the maintenance there. In any case the particles of silt sand which ever were in my opinion fine enough to get through that filter. But in Straubing they did find a lot of junk that was coarse enough which did not go through. He said it was full. What does that mean? I wish I was there.

But I was there when the fuel pump was taken apart and large amount of silt like gritty particles were in the pump as well as the Fuel control unit.

I really dont think the fuel filter is fine enough to capture all of it. I guess the reasoning there is its better to have some fuel even if bad, than no fuel if the filter gets totally clogged.

How did it get in there? There could only be 2 possibilities. 1 I got bad fuel from the airport A right afterwards flew 1/2 hr to airport B where I took on 80% more gas for a 2 hr flight.
I noticed something strange with my fuel system about 1/2 hour after departing airport B. It could take that much time for it to have gotten enough junk into the filters to allow it to become clogged. So can I say for certain where I got the bad fuel?

The least likelycause in my mind is Sabotage. While I put the odds at a very low probability I cant completely rule that out.

Remember I sump before each flight all drains and found nothing.

So I got Mr Funnel standard initially. Later got the largest capacity cause the original one was too slow. Fueling 380 Lts can take some time. However, in order to use the larger capacity funnel with high flow rates I had to improvise a lip onto it. This way the fuel as it was swirling around would not come out.

No matter what its tedious and a pain in the butt. Especially when trying to top off because of the possibility of overfilling. But you do have peace of mind afterwards.

The security tape is a tape that if disturbed will show void on it. I fly with it up to 190 kts and it wont come off even if using TKS. Thats descending just to clarify, that way I wont get wise crack comments.

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