My '81 308 GTSi. Starts just fine when cold. Let it run until warm, shut it down, wait a few minutes.... no start. So today I hooked up a CIS pressure tester and found the problem: cold control pressure is fine, warm control pressure is fine, but when when I shut the motor off the system kinda holds pressure for maybe 60 seconds and then it drops to zero. This isn't a slow leakdown - the needle on the gauge is in freefall. Searching here says that I should be replacing the accumulator, but reading the Probst book and looking at websites dedicated to other CIS cars suggests two other possible problem areas: the fuel pump check valve and the o-ring in the system pressure regulator's push valve. Does my symptom suggest one of these over the others? I'd as soon not throw a new accumulator at the problem without a good reason. (Injectors are all new as of last year; thermotime switch is new and checks out; cold start injector is spraying when it's supposed to and not otherwise; car started the first time I turned the key after replacing belts, replacing outer cam drive bearings, degreeing cams because I'm a compulsive motor nerd, replacing plastic over steel cam sprockets with metal, adjusting valves, sacrificing a black goat to the Ferrari gods at midnight, ....)
Sounds like the check-valve. That's precisely what it is there for: To keep some amount of system pressure when the car is off. After that, the accumulator. If the car is US spec, you'll have a little hose connected to the accumulator which goes back to the fuel tank. Wonder if it's wet in that hose? If so, failed accumulator.
this ! take off the small hose going from the back of the accumulator to the tank - if fuel comes out, diaphragma of the accumulator failed - 70% chance since pressure seems to drop so fast if dry, "non return valve" of the fuel pump fails - 30% chance . . Image Unavailable, Please Login Image Unavailable, Please Login
My WAG: It is the check valve slowly leaking back into the gas tank. Why does it take a minute to see the fuel pressure drop? Because that's how long the fuel accumulator takes to bleed down. It could also be the fuel accumulator slowly leaking out the vent. Checking that it a good idea. Euro (and poorly maintained US cars) have a feature where it pisses fuel onto the ground to let you know it is unhappy.
Yep, I'm thinking the same thing - accumulator is doing its job, check valve is not. The Probst book suggests that a leak at the o-ring back at the press valve in the system pressure regulator could produce that effect as well, but that's an easy check while I have the CIS tester installed. There is no fuel under the car, so if the accumulator is losing fuel, it's losing it back into the tank the way it's supposed to.
nope ... it should not loose fuel ...if you take off the hose and it leaks ... it`s time for a change
I think you guys might be mis-communicating a little bit. If the system is losing fuel back into the tank via a leak in the fuel pump check valve or via a leak in the pressure regulator section = accumulator OK and doing it's job. If the system is losing fuel back into the tank via the accumulator drain port and drain hose = bad accumulator. On a US version, fuel (wrongly) coming out of the accumulator drain port won't reach the ground (because of the return drain hose to the tank -- euro version don't have this return drain hose). Remove that return drain hose and then recheck as Michael suggested: no fuel coming out of the accumulator drain port with the engine running = accumulator OK; if fuel comes out the accumulator drain port with the engine running = accumulator bad.
Well, it's a good thing that replacing the accumulator helped your problem. To expand on this though, the more common cause of a drop in rest pressure is a small o-ring on the Primary Pressure Regulator in the fuel distributor. This valve regulates lower chamber pressure by sending fuel back to the tank for a more flexible delivery of fuel throughout the RPM range. It does so by moving the valve back and fourth through a small orifice and is controlled by the CPR/WUR. When the engine is shut down, the spring closes the valve, thus sealing the return to the tank. The in and out motion and age of the o ring on this valve usually causes the o ring to split leading to inadequate sealing. Symptoms would be the same as a bad accumulator (popping noise coming from the accumulator). Leaking injectors can cause this too Next time there is a warm start issue, check to make sure the injectors are not leaking. If not, pull out the PPR from the distributor (pictured) and replace the o ring with a viton one. You can get an assortment from Harbor Freight for >$10 and have ~25 at your disposal. If that doesnt work, only then replace the accumulator. P.S. Getting the plunger may be hard if there is residual pressure, so a good hook pick is your friend Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Hi guys! I can't find the Primary Pressure Regulator in the fuel distributor in the official schema.....may you help me to find out where is it in this schema? Is the pressure regulator just for USA version or has to be also in euro version? many thanks!! Eurospares | Ferrari 308 Quattrovalvole (1985) 010 Fuel Injection System - Fuel Distributors, Lines
Thank you so much but i was searching for the item in the pictures above, not the warm up regulator....but the item indicated by the arrow. Thanks so much!
That is part of your fuel distributor, item 1. The primary regulator is internal to that distributor. Nothing you can do with it.
The primary fuel pressure regulator on the Ferrari K-Jet systems is considered to be a part of the fuel distributor (on all versions) -- so it isn't shown as a separate spare part in the Ferrari SPCs. You might have a look at some of the Porsche, MB, or Volvo part suppliers to see if they can supply individual components of the K-Jet primary fuel pressure regulator if you need something. As Michael showed in post #9, the seal (o-ring?) on the end of the primary fuel pressure plunger has a secondary function to seal the fuel return path going back to the tank so the residual fuel pressure does not (wrongly) go to zero when the fuel pump shuts off -- are you having a problem with getting the proper regulated fuel supply pressure when the fuel pump is running, or keeping the proper residual fuel supply pressure when the fuel pump (engine) is shut off?
Thanks guys! My case is the same of the original post, the car start perfectly when cold and needs few seconds when warm. I will check the pressure at the accumulator but it has no more than 10 years so i was thinking about other issues and found out the oring of the posts above but i can not find where it is in the schema. Thanks so much!
You should really measure the residual fuel pressure at engine shutoff to confirm that having no residual fuel pressure is causing your warm restart trouble. The usual repair order process (if no residual fuel pressure is the trouble) is: 1. Check for liquid fuel coming out of the vent nipple at the rear of the Accumulator when the fuel pump (engine) is running -- if no liquid fuel is coming out = the Accumulator is probably OK. If liquid fuel is coming out = replace Accumulator. (Some version have a hose on the vent nipple, and some do not.) Image Unavailable, Please Login 2. Replace the check valve on the fuel pump outlet. On some CIS fuel pumps, the check valve is a non-replaceable part of the fuel pump itself so requires buying a new fuel pump. On later version CIS fuel pumps, the check valve is a replaceable part. (So you first need to determine which type of CIS fuel pump you have -- many get changed so don't assume the fuel pump shown in the SPC for you car is what is actually on your car now.) 3. Replace the end seal in the Pressure Regulator. Have you done #1 and #2 already?
Thank you so much! I will start with the check next week starting from the accumulator. I really don't know at the moment if I have a fuel pump with or without the non return valve. Again i don't understand where is located the oring in the pressure regulator watching at the last picture of crocket post...
I am also experiencing hot start issues. Already have a new accumulator to replace. What is mentioned in post #9 also applies to 328s? Is this PPR easy to remove and relocate? I’m worried it should need some torque or adjustment. Anybody knows the o’ring diameter? thanks in advance.
Yes (but Euro and US 328 use different fuel distributors). In almost every K-Jet reference that I have, the fuel pressure regulator section is drawn in the figures in a sort of stylized form to help understand the fuel flow rather than being its true physical form. This figure from the Probst Bosch Injection Book is the best one that I could find: Image Unavailable, Please Login There's no super-critical torque spec for reinstalling the fuel pressure regulator, but you should use a new/reannealed (i.e., soft) copper sealing washer, and it does need to be tight enough to not leak. My guess is that Ferrari doesn't even give a separate tightening torque for it since it is considered to be part of the fuel distributor (and not a separately replaceable component). You could match up the thread size/pitch of the large hex fitting to another injection component with the same thread size/pitch also using a copper sealing washer in Chapter M of the Mondial8/QV WSM to get in the right ballpark (if uncomfortable going by "feel" ). Additionally, might be a hassle to even get a torque wrench on it in-situ...
