Hi All, My Air injection system plumbing appears to be seriously screwed up and I'm trying to follow the diagram in this link. https://ferrparts.com/diagrams/355-2-7-motronic/air-injection-device-008 Could anyone tell me where pipe 37 goes to. This supplies the vacuum to the accumulator tank but I am trying to trace where it connects. Any help would be appreciated. I've had my 355 Spider since 2007 and the secondary air injection has never operated and I have had the exhaust bypass wired open for 5 or so years. Now I have more time on my hands I am trying to correct the odd bit that' isn't correct. Cheers all.
@yelcab Many Thanks my friend. I don't suppose you know how the pipe routes from the throttle body to the vacuum tank. I must have that pipe hanging loose somewhere
Check your... check valves #20. If only one fails then there will be no vacuum build up in the vacuum tank and that will lightly mess up with the fueling. BTDT. Testing the system with a mityvac allowed to me to rule out any leak.
@Timmo , cheers - The feed to the vacuum tank is missing altogether so wanted to correct that first - just can't work out the pipe route from the throttle body to the tank - Is it piped just from the right hand side? . The car is running smoothly and passed all emissions
Yes, basically. Hard to describe without a picture but the hose is somehow routed longitudinally, to the right and below the fiberglass heat shield below the RHS MAF, assuming your F355 is indeed a 2.7.
Pipe 22 goes to the left hand side. You can see the white T-piece in this photo below the blue plug: Image Unavailable, Please Login You can just see the LHS black and white check valve on the far side of the oil filter.
The T on the diagram, which shows the RHS TB assembly, is not oriented correctly, as confirmed by the picture of the engine bay.
That's a photo of a 2.7 from the forum. Unfortunately, I'm not near my 5.2 at the moment and can't tell you if the routing is the same as mine. I can't remember the pipe running between the oil filter and the oil pressure sender. Most cars this age have gone through a few engine-outs, so the plumbing may have been disturbed a few times.
It is a hose, not a pipe. Left and right intakes meet at the T, the remaining T connects to a hose that runs along to the right side of the engine bay, then back toward the vacuum can. It then connects to the short hose (that actually goes to the can) via a small hard plastic hose-to-hose jointer.
I took the dimensions of a joint in the hose at this point… Image Unavailable, Please Login Image Unavailable, Please Login The standard hose may be 3.5mm (ID). Does silicone stretch more than rubber? The hose was slightly loose, but that may have been age.
Back when those were still production cars we had very poor experience with silicon hose down there. It does not take the heat as well as more conventional hose and we were forever replacing cracked hoses.
It does; right up until it doesn't. I've had many silicone hoses split when installing them. They seem OK as long as you push them onto the barbed fitting 100% straight, but if you put even a little side load on the hose it can just split without warning. Whereas traditional rubber vacuum hose may go on a little harder, but will not split like that. If you need to "make" any of these hoses fit when they feel slightly too small, a few seconds with a heat gun will work wonders to soften them up.
Many Thanks to all that have commented. I have now located the hose from the t-piece and connected that to the vacuum tank. Prior to connecting I ran the engine and there is a very weak vacuum at idle - like enough to hold a sheet of paper to the hose but not much more. Should the vacuum at idle be that low? I also pulled one of the hoses from the connection to the throttle body (ie before the check valve) to see if the vacuum was any different and it wasn't. I am planning to connect a vacuum gauge to the second vacuum tank hose and take the car for a run to see how much vacuum is generated when i come off throttle and to see if that leaks down. I'm not mechanical at all, so wanted to ask if this is sensible. Again I really appreciate people taking time to comment.
There is too much valves overlap (when intake and exhaust valves both open) in the 355 such that there is not a lot of vacuum. However, it should be more than "holding a sheet of paper". Hook up a vacuum gauge to it and see what that psi value is before you can pass judgment. There may be a leak, or the one way valves may be broken, or ...
Your in good hands with yelcab I would say that’s not enough but that’s a very subjective test. Gauge it
Thanks again - so I hooked up a gauge from the vacuum tank - on cold start idle the vacuum measured 10 inch/hg (5 psi). On stopping the engine the vacuum slowly dropped over 10 mins. I don't know if this is acceptable or if i need to find the leak. I then drove the car, on and off throttle to see how high the vacuum would go and the result was 22 inch/hg (10.77 psi). Strangely, after the car was up to temp, the idle vacuum dropped to around half the value I saw on cold start (5 in/hg or 2.5psi). Can anyone advise if these figures are normal. I assume they are low as the Capristo exhaust valve I was looking at purchasing requires 0.7-0.8 bar (around 10.5 to 11.6 psi) at idle to close the valve ( as the capristo operates vacuum to close rather than open (ie reverse to OEM). Again, thanks in advance for any input
I didn’t take them off and check flow but as the vacuum was holding it suggests that they are not allowing flow back. If my psi figures are low then I guess one could be seized and the vacuum not getting through. Getting to the left bank back on need smaller hands I’ll check them tomorrow but does anyone know what psi is required to open the exhaust valve
