Hi all, I have some questions regarding the fuel pressure. My car has severe problems starting, and was running rough when it last did. Now I do not even get it started at all. Crancking goes well, but it does not start, not even on less cylinders. As the (new) plugs are still clean or only mildly brownish, and I do not smell gas, I suspect a fuel problem. But where is the best way to start measuring the pressure? According to the WSM, there is a connecting point underneath the plenum chambers, but I do not see it. The rails only have the 2 normal connecting points for the fuel lines as far as I know. So instead I connected to the valve which sits on top of the (replaced) fuel filter. It only gets to 13 psi where 40 would be normal. Or does the 355 have a lower pressure at that point (not likely)? If that point of connecting is the right one, and 13 psi hence is the correctly measured value, where to start looking for clues first? It means there is pressure, but not enough. All injectors leaking is not likely, so I would suspect a partly malfunctioning pump? Or properly working only part of the time? Car is a single pump 97. Of course I can try to measure at the fuel line coming out of the pump itself, but before I do that and spill a lot of fuel in the process(dangerous), I would check with the experts first. Thanks for your insights!
I know your question was regarding fuel pressure but. Have you ruled out the pair of crank position sensors? When they go bad it causes the same symptoms.
I don't think there are many places you can easily hook to other then the schrader valve. It should have had a cap on it and a valve stem inside like a car tire. If you're hooked to that one you've got the right spot. You need to remove the valve with a valve stem removal tool if your hookup doesnt have a part to depress the valve. It you're hooked up anywhere between the pump and the fuel pressure regulator you should see about 45psi. With all your injectors wide open the pump could still keep over 40 psi on it so you're right that's not it. If your pump is definitely running enough to get you 13psi consistently and your fuel filter is new as you stated then I'd have to say your pump is the issue. Probably the melted rubber gasket issue. You might be able to rebuild it.
That's right, I forgot. The 355 needs to see rotation before it turns the fuel pumps on doesn't it? 96+ should only have one crank sensor since they went to one ECU. Still if you can bleed off the pressure, then crank it and it goes back to 13 then it must be getting position to turn the pump on or it would still be at 0psi. So if your pump is running and only making 13 then it's done for.
Thanks 97 spider, Jackie and or Bill. I have indeed hooked it onto the schrader valve, but as I have a very complete set I can hook it up anywhere I want (theoretically that is). Most cars have a valve on the rail, and the WSM had a drawing where the connection was somewhere underneath the chambers, so it got me doubting. But now we know the way of measuring is correct. In the mean time I have connected 13V-14V to the pump directly, and it now goes up to 17 psi that way. I did not try to start it as I need at least 30 psi (I think) to get it started. And obviously this is a problem I need to solve before I can safely start it. Other remarkable thing, it does not keep any pressure at all, not even 1 psi. When I turn off the power, the pressure immediately drops to zero. What else besides a fuel leak in a hose (which I do not have) and a faulty accumulator can cause this? (but a faulty accumulator does not prevent building up to 40 psi as far as I know). Pulling the pump is one thing I best save for last...
Just remembered, i had the same fuel problem years ago. Hard to start due to pressure problems. It was the fuel pressure regulators, there is one at the bottom of each fuel rail. These hold the pressure of the fuel while the engine is turned of which allows starting straight away. So when mine went bad it was a bugger to start. There very easy to change. Your fuel hose that sits above your rocker cover conects to it, so thats how you find them. JUST TOOK A PICTURE OF ONE OF MINE TO HELP YOU LOCATE THEM. Image Unavailable, Please Login
Thanks! Did you by any chance measure the pressure back then? As far as my fuel injection knowledge goes, the pressure regulators make a difference of around 5 psi? Or is it much more when starting the car? I will do a volume test on the pump this evening to see what comes out of it. When it is half a liter over 30 secs, it must be (one of ) the pressure regulators I guess.
The fuel pressure regulators are back pressure valves that hold the right amount of pressure on the rail no matter how much fuel the engine is using. At idle your pump my be able to hold say 60psi but instead of the rail being that high a pressure the regulator opens up at around 45psi and let's the excess fuel/pressure bypass back to the tank through a return line. You pump is always putting out more then your engine would be needed at wide open throttle and bypassing the excess back to the tank. A bad FPR could indeed be the problem if it's not holding back pressure especially with the immeadeate bleed down info. If you can plug your return lines and see if the pump will pressure up the way it should.
Ok, I will try that next if this is not the culprit: In the mean time I have measured the output volume of the pump, and it was a little less than 200 cc in 30 seconds. ( so it will take the pump 2 and a halve minutes to output half a litre (= a pint). That is way too little, so for me that points towards a malfunctioning pump. Do you agree? I guess that there is no other next step than emptying the tank again and dropping the pump... I have read a lot about the molten rubber sleeves and gaskets today, and when I flushed the tank earlier, indeed black particles flushed out. I was happy at the time (I did well flushing it, look I flushed something out, jay ) Now I suspect it was the proverbial tip of the iceberg. It looks like I will encounter some serious black mess...
No i didnt measure the pressure, i just knew after investigating that one of the regulators was not holding pressure, thus the car was a sod to start. Some times it would but most the times it didnt. I changed both regulators with bosh items not bought from ferrari, they were 30% of what i would have been charged by ferrari. Hope you get to the bottom of this.
So I drained the tank, and disconnected the fuel line connectors. (the electrical connections I already removed for running the pump directly on a battery.) Then off with the 10 mm nuts, and it did not come off. I noticed some red sealant on the edge, so with some gentle persuasion I was able to split that seal, and wiggle the pump out. Here is how it looked, not very good. You can see that there was an extra silicon sealant used, which is not normal. And the pump itself looks to be at an angle: Let's investigate further: Image Unavailable, Please Login
I disconnected the bolts that hold the out canister in place, and I disconnected the power supplies. One of the fuel lines had been replaced by normal fuel pipe. You know, the type that has fuel resistant inside, but NOT on the outside!!! Needless to say that was falling apart... Image Unavailable, Please Login
But the real horror was yet to be unveiled. The inner rubber holder was, well, dissolved... Looks like someone has been here before, someone without any detailed knowledge about rubber and fuel... And there is another thing that is shocking, do you spot it? Image Unavailable, Please Login Image Unavailable, Please Login
The pump underside has been "worked" on, so it would able to stand in the canister, even still at a small angle. No "ninja-star" rubber underneath, and a pump that most likely is not the correct one... Size most likely ok, but I am not sure. With all the dissolved rubber everywhere, I suspect that the pump is internally partly blocked as well. Capacity was only a third of what it should be, I guess that is explained now... Anyway, looks like I better buy a new complete pump assembly... And so I just did. To be continued! Image Unavailable, Please Login
Scary. Hopefully the filter stopped all this garbage getting to the regulators and fuel rails. Did you check the filter, Robbe? I'd be ordering one with the new pump.
I already replaced the filter , and checked if the new filter had picked up particles, which it did not really. So that is why I had to remove the pump as the problem of low volume was not in the filter... The injectors I had professionally tested and cleaned and the rubbers and caps replaced not too long ago when I did the major. So I will check and rinse the fuel supply to the filter line, the connection between the filter and the pump. With that done and the new pump installed, I will check again for pressure and volume. If all goes well it will deliver as should. If not I am puzzled again...
Interesting improvisation job by the PO. The pump is from some other car or "universal", possibly (originally) of the correct presure and flow. With regard to the silicone sealant, it is only good to make a mess and the pump removal difficult. You don't need any sealant there, just use a new o-ring.
Final update: I received the new pump assembly, and installed it. I turned the key, and watched the pressure rise to around 4 bar , 55 psi when she started! Pressure immediately dropped to 3.6 bar, around 50psi. When revved, it does not come over 3.8 bar as per spec of the pressure regulators. So these are working as they should. The initial higher pressure I contribute to the fact that the whole system was empy when I started crancking. Happy! Now up to that next task, the dreaded SDL... Think I will start with fooling the system with the 1.5V battery trick to see what happens. As it is a 5.2 I do not know which side... But that is for another posting!
Glad you got it sorted, and thanks for the fuel pressure numbers, i will compare to mine as I have the "start then stall" issue (although it runs fine when restarted)
Check and see if you have any pending OBDII codes - you may and that may give you and idea of bank 1, bank 2 or bypass.
Would someone mind posting the link to the thread about the dissolving seals on the fuel pumps, not having any luck finding it with the search engine. thanks!
Here you go. http://www.ferrarichat.com/forum/348-355-sponsored-bradan/489961-348-1995-f355-owners-you-concerned-about.html?highlight=348+fuel+pump+gasket
I have a euro 1997 5.2 , so only accesible from the connector next to the ecu. (by the way, no bypass sensor as far as I know?) I do have a universal reader, but have not tried to make a connection with it yet. The 1.5v battery trick I can use for the same purpose: - instead of the cat ecu, connect a 1.5v battery to the signal wire to fool the ecu. When for instance I do that on the left side, and the light goes out, I know that it is that side. If not I will switch to the right side. If all goes accordinbg to plan, I know which side is working and which is not. Then I can try to swap the ecu's (+ help the side which lent the good ecu with the battery trick), and see if the sdl goes away. If not, the problem is in the thermocouple. If the sdl goes away, it is the (other) cat ecu. Why not try to pull the code you think. Because a lot of OBDII readers have trouble connecting to this ecu. And to keep buying readers until I hav efound a working one, is a bit ridiculous. Or does anybody know a brand of reader that is easily available in Europe, that actually works?
