Gradual loss of power

Dark Skies · 01-05-2009, 02:13 AM

Just throwing this recent problem out there to see if it seems familiar.

On my regular drive to work there is a short slip road onto a busy motorway. Traffic is going at 70 - 90 mph. Unless you're prepared to accelerate pretty hard and swiftly get through the gears you're never going to get onto this road during rush hour.

Anyhow About three weeks back I noticed under hard acceleration that it felt that I was hitting a flat spot at around 65 mph. It was more of a feeling rather than anything actually noticeable and higher speeds seemed unaffected under regular driving. It stayed like this for about a week.

About a week after that I noticed cruisng above the 70 mph mark would bring on this flat spot. A week after that and hard acceleration has this flat spot coming on at 45 mph and cruisng beyond 50 mph is impossible. regular city driving at 30 - 45 mph is unaffected.

I reckoned this was probably fuel starvation - compression and head are in good shape as the engine has only done 82,000 genuine miles and was pampered by the previous owner. The car was due a basic service so amongst a lot of other stuff (see list) I replaced the fuel filter.

Other stuff that was replaced:

rotor
distributor cap
all plug leads
spark plug
oil filter
oil
air filter

I figured that the fuel filter and air filter being replaced would have fixed the problem but it didn't. This is my regular driver so I need to get on top of the problem pretty quick. I have a brand new fuel pump sitting on my workbench that came with a load of spares that the previous gave me. However the fuel pump on the car at the moment sounds very quiet (gentle hum) and looking through receipts was replaced back in 2005 just before it was sold (it had been standing a while I think). The car has been regularly driven without problems since November 2005 (it had 62,000 miles on it !!!!).

Someone suggested to me that it might be the Air Flow Meter (attached to air filter box) playing up. I know these can be taken apart and tweaked to avoid wear tracks but at 82,000 miles this seems unlikely to me. I had a 400,000 miler in the past that was still going strong until a drunk driver totalled it and that had the original unadulterated air flow meter in it.

I learnt that there is a filter in the petrol tank - a fine gauze type that can be cleaned. I've never had to do it on any of my other 944s but this seems more plausible under the above symtoms.

Anyone else got any ideas?

The car is a bog standard 2.5 litre from late 1983

Tishabet · 01-05-2009, 08:27 AM

I'd take a look at the throttle position switch.

Dark Skies · 01-05-2009, 04:03 PM

Certainly worth putting on my to do list.

Dark Skies · 01-10-2009, 12:30 PM

Just got around to draining my fuel tank and pulling the strainer. This is what 26 years worth of crud looks like.

And this is what it looked like after a good blast with carb 'n' choke cleaner.

When I was draining the tank the fuel didn't flow as quickly as I thought 12 gallons of fuel might. I'm hoping this will have resolved my acceleration problems.

Rocket · 01-11-2009, 06:12 PM

This is the K Jet system? I doubt very much it would be a fuel distributor issue. I would pull the injectors and give them a clean too. K Jet is pretty straight forward to fault find, and easy to measure fuel delivery etc.

Anyway, I've come here today because I stumbled upon a picture of your Hensen. Have you still got it? If so I'd love to see it.

Where abouts in the country are you? Near East Yorkshire and I can help you with your fuel problem. I have a SnapOn fuel pressure tester master kit and Autodata info from the era of your Porker. Pretty familiar, though a little rusty (pun intended) with K Jet. Be glad to help for a go in that Hensen

I'm here.....

seanpepper at gmail dot com

Rocket

Dark Skies · 01-12-2009, 12:16 AM

Quote:

Originally Posted by Rocket

This is the K Jet system? I doubt very much it would be a fuel distributor issue. I would pull the injectors and give them a clean too. K Jet is pretty straight forward to fault find, and easy to measure fuel delivery etc.

Anyway, I've come here today because I stumbled upon a picture of your Hensen. Have you still got it? If so I'd love to see it.

Where abouts in the country are you? Near East Yorkshire and I can help you with your fuel problem. I have a SnapOn fuel pressure tester master kit and Autodata info from the era of your Porker. Pretty familiar, though a little rusty (pun intended) with K Jet. Be glad to help for a go in that Hensen

I'm here.....

seanpepper at gmail dot com

Rocket

Hi, this is the fuel strainer in the tank just downline of the fuel pump. It was totally clogged and starving the system of fuel. It'd obviously been slowly and stealthily strangling the system for some time before it got to the point of being noticed. Acceleration and top end have been transformed!

As to the Hensen... unfortunately I sold it about three years back. Too bad too because I miss it. The new owner doesn't appear to have put it on the road either - I checked the DVLA's online tax site.

Rocket · 01-12-2009, 11:13 AM

I saw that fuel filter. Glad you got it sorted.

Don't suppose you have any contact info for the person who bought the Hensen? I'd like to have a go at owning one myself.

Thanks.

Dark Skies · 01-12-2009, 11:22 AM

Quote:

Originally Posted by Rocket

I saw that fuel filter. Glad you got it sorted.

Don't suppose you have any contact info for the person who bought the Hensen? I'd like to have a go at owning one myself.

Thanks.

There's an owners club but it doesn't seem very active.
http://freespace.virgin.net/hensen.m30/index2.html

There's usually one or two at the Stoneleigh Kit Car show during the May bank holiday. Only 17 were made and that was way back in the eighties.