Porsche 924 fuel pressure test

Porsche 924 fuel pressure test - part 38

Рет қаралды 331

2 ай бұрын

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That's right, we are back on the infamous Porsche 924 fuel system! This time we are testing the fuel pressure to see if all the parts in the system are behaving as they should.
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Пікірлер: 20

@Witty924 2 ай бұрын

Hi Everyone, I appreciate all the great comments and feedback. I need to update you on a mistake I made on the video. I have realised that I had the pressure test kit set up the wrong way round. The switchable valve should be after the gauge reader. This is important because you can measure system pressure at 75psi/5bar and then control pressure at 51psi/3.6 bar by switching the value to a closed position. I have re-run the test and confirm that I do have low pressure and when you close the valve, the pressure drops to a regulated pressure of 3 bar 41 psi. So I need to raise the pressure with a fix on the WUR. Thanks for the understanding everyone 👍

@Danny380bhp 2 ай бұрын

No mate you did have it set up correctly in the video. The tap goes between the WUR and the gauge. (Haynes manual calls the WUR the control pressure regulator too) Closing the tap checks system pressure as stated on page 77 paragraph 8 of Haynes manual.

@Witty924 2 ай бұрын

@@Danny380bhp thanks Danny, so I took the WUR off, cleaned it up again, no blockage found, I also adjusted for warm/hot pressure and I got a reading of 52 psi but with the pressure kit set up as stated above in my pinned comment. So I thought I was out of the woods. The car is running well, I took it for a 5 to 10 mile trip, all good. I have a long trip this weekend so I will keep an eye on things and fuel mpg. Got to love the old classics haha 🤞👍🚙💨

@Danny380bhp 2 ай бұрын

Just remember that the WUR and Aux air valve are just devices that aid the warm up of the engine (act as a choke) and that once the car is at operating temperature they are no longer doing anything at all. When at operating temp - WUR is closed and no longer flowing fuel through & Aux Air valve is shut completely. Gotta love the classics!

@Witty924 2 ай бұрын

@@Danny380bhp we are on the same page. The adjustment I made was to ensure it was definitely closed when warm/hot. I did the test and adjustment on the AAV so that is operating as it should be. Have you ever tried adjusting the pressure valve in the fuel distributor unit?

@Danny380bhp 2 ай бұрын

@@Witty924 there’s no need to adjust the shims on the fuel distributor if you have good system pressure imo

@pauljohns3186 2 ай бұрын

You have to love the classics, they always keep you busy 👍

@timmiller4130 2 ай бұрын

Great video, Whitty! I would love to see you do a video on how to modify the WUR. There are a few written articles out there on how to do it but a video would be so much better. Also, I have that exact same testing kit and it leaked terribly from every connection. I think I spent more time trying to stop the leaks than I spent testing my pressures.

@Witty924 2 ай бұрын

Hey Tim, thanks for the comment and support. Next video I will cover the modified unit that I have done, I need to get a decent close up of the modification 🤞. Good spot on the test kit, I picked it up for £35, I added some of my own rubber o-rings which seemd to do the trick, as you said, my first test I created a small fountain 🤣

@Fatcatbaz 2 ай бұрын

Great to see another 924 video. Just an observation/question, when you turn the ignition key from off to on the fuel pump should prime the system. Usually last for 1 to 2 seconds. This is ahead of you engaging the the starter via the key. It could be irrelevant, but I didn't see the ignition on prime the system. Easy to check, just turn the key to on without switching it to start. You can do this more than once to see it it primes. Might not be part of the running problem, but will impact the start up. Is it worth checking? Baz

@Witty924 2 ай бұрын

Hey Baz, thanks for the comment and support. You make a good observation, so I believe on later cars the prime happened on start up but that maybe the bigger engine 2.5. (Might be wrong). Also it can depend on the fuel relay that you run, I think some have an extra pin which sends power to.prime on the first click of the key turn as you say. I need to double check what fuel relay I have, it would certainly help on the initial starts 🤞👍

@Danny380bhp 2 ай бұрын

Hi mate, your incorrect. Control pressure should be low when cold and then gradually raise as it warms up. When warm it’s at system pressure which is 5bar. Page 77 of Haynes manual shows graph with pressure raising from cold to hot. Warm up regulator transmits low pressure to plunger/air sensor plate when cold which allows the plate to raise higher and send more fuel to the injectors when cold (simulates a choke) As it warms up, pressure raises and it pushes down on plunger/air sensor plate which reduces the extra fuel to the injectors. Also 12v feed to warm up regulator just heats bi metallic strip quicker which raise fuel pressure quicker. If you were to unplug it would essentially take longer to raise the fuel pressure to plunger.

@Witty924 2 ай бұрын

Hey Danny, thanks for the comment. This is why KZfaq is so great 👍. So with the pressure I'm getting would you say things are working correctly? I didn't think the pressure should be so high? Having read a few forums and watched the classic wheeler dealer episode with Ant, there seems to be varying views on pressure. I checked out Haynes and read the part you mentioned. It says the system pressure of 65 to 75psi which would suggest I'm in spec. But as you say cold pressue as the graphs suggest a starting pressure of just 20 to 30 PSI roughly. Any thoughts welcomed 🤞👍

@Danny380bhp 2 ай бұрын

When the WUR warms up it essentially closes the flow through it and raises the pressure to system pressure on the gauge. IF the warm up regulator was blocked or stuck shut you would see system pressure at cold. I think yours may be blocked.

@Witty924 2 ай бұрын

@@Danny380bhp Thanks Danny great suggestion. I have refurbished this WUR, so I need to inspect it again and see if I have a blockage. The inlet gauze can sometimes be a potential area for debris to experience blockages. Have you seen any other examples of WUR getting blocked up, I want to save myself from ripping it apart again 🤞

@Danny380bhp 2 ай бұрын

@@Witty924 the best thing is to remove the gauze completely and fit a 6mm x 10mm filter inside the banjo bolt itself. You can never get the gauze fully clean. I got my filter from mrinjectoruk

@chrismadge7292 2 ай бұрын

@@Witty924 I was going to say the same but Danny beat me to it. If the bimetallic strip resistance is in spec, and the WUR has power to it, then its probably crap that accumulated in the little mesh screens in one of the fuel outlet/inlets. Easy enough to clean, a lot of people do away with the screens as they are prone to blocking. The adjustable WUR is a mod I have done and its quite handy but it only works in one direction. I cant remember if it increases or reduces the control pressure. But if you need to go in the other direction you have to take the WUR out of the car and manually adjust the position of the fuel cell.