83 308gtb qv New starter a year ago, high torque from classic car performance. Half tank of gas and it takes a bit of grinding (seems like an eternity, probably 10-15 seconds) the starter before it fires up, then runs fine. If I fill the tank, the next series of starts occur barely with twist of the key. Any ideas on what the culprit might be? Appreciate any and all insight Sent from my SM-S918U using FerrariChat.com mobile app
Fuel level in the tank shouldn't have any effect on the amount of starter motor cranking required to start up the engine on a K-Jet model -- but the residual fuel pressure falling too quickly after engine shutoff can make warm restarting difficult (while cold starting after long disuse can be OK). With a 1/2 tank of gas, do you have this problem on the 1st (cold) restart of the day after letting the car sit overnight?
If the fuel pump's check valve is good and the accumulator is functioning, then the high pressure side of the system maintains pressure when the engine shuts off, and the tank is isolated. Wouldn't matter what the tank level is. But if the check valve has failed, then fuel can drain back into the tank. Or if the accumulator diaphragm has failed, then fuel will drain back to the tank (or onto the ground with a Euro car). I can see fuel tank level possibly factoring into those scenarios. Theoretically a full tank would let less fuel drain out of the system than an empty tank, and would factor into how long the pump has to run on the next startup before fuel reaches the injectors. I think accumulator failure is pretty common based on reading here on the forum. The one on my 1987 328 was definitely shot, and the confirming diagnosis was finding fuel in the accumulator vent line. It means the internal diaphragm developed holes or a tear. I replaced the accumulator, and also put in a new fuel pump while I was in there (the old one was leaking at the check valve and had a corroded barb on the tank end, and for under $100 I figured why not do the pump while replacing the accumulator since they sit side by side). After that work, my cold start cranking/starting time was reduced from about 4-5 seconds to instantaneous, even if I haven't driven the car for 2-3 weeks. These issues can also mess with a warm start since heat from the warm engine can exacerbate the issue. But there are other causes for warm start issues too. For that matter, there are other causes of cold start issues. You have to start looking at the big picture and correlate things to work up a diagnosis.
Try replacing your cold start relay, that's solved the problem on my 3.2 Mondial, the fuse box is the first place I go if there's a problem with my car! Alden
Didn't drive my car yesterday. Came out this morning, got in and a twist of the key fired up immediately. Back history: Accumulator replaced 6 years ago. All relays replaced 9 years ago. Turtledriver fuse board. I have spare relays and will swap that to see if that addresses the issue. Will have to order a new accumulator, good to have a spare in the pocket anyhow. Thanks for your thoughts!!! Sent from my SM-S918U using FerrariChat.com mobile app
The Accumulator is only one of the three things that can cause the residual fuel pressure to fall too quickly (leaky Accumulator, leaky fuel pump check valve, or leaky o-ring in fuel pressure regulator plunger assembly) -- and you can easily rule the Accumulator in, or out, by just checking for fuel coming out the vent nipple on the end (by removing the small rubber line going back to the tank). However, better to actually measure (or have measured) the residual fuel pressure to know if you have a problem that needs to be fixed before throwing parts at it -- JMO. PS A good cold start-up shows all the relays and electrical stuff is working OK.
I bought one of those cheap k-jet fuel pressure test kits I read about here but sat on it for about a year as the fuel system mystified me a bit. Already had a box of copper washers (and good thing as once I cracked the system I needed to replace a few) but it was so much more simple than I had thought it was going to be and revealed a WUR problem on my car… I had replaced a leaking check valve and fuel accumulator as well as all the injectors. Fuel pressure test will tell you lots. jay
One thing to consider... many times a fuel system problem turns out to be an ignition problem. I spent months going through the fuel system to troubleshoot an intermittent warm start issue. Turned out it was a slowly cooking RPM sensor, cutting out the ignition.
This is the one I used: https://www.amazon.com/Tool-Aid-33865-K-Jetronic-Injection/dp/B0002SR5NU/ref=pe_386300_440135490_ci_mcx_mi_sccl_2/139-7215952-2319241/ref=ci_mcx_mi?_encoding=UTF8&pd_rd_i=B0002SR5NU&psc=1&pd_rd_w=dCCvk&content-id=amzn1.sym.e8f5a9d3-51d6-473f-aa67-49440df946f6&pf_rd_p=e8f5a9d3-51d6-473f-aa67-49440df946f6&pf_rd_r=K12FBPN47C3KRCJXST32&pd_rd_wg=C4t9S&pd_rd_r=9d2bed6e-473e-4b46-9b13-f32e5d91ffda and I had a kit of various copper washers that I had to use a few from.
