I’m hoping the community can offer some ideas on a problem with my engine. It’s a 2005 Suzuki GSXR 1000 in an autocross-only sports racer (a Cheetah). This is the 3rd year running this engine. Had cooling issues in previous years but those have been resolved. A new problem began this summer. In the first few runs of the day the engine is fine. But as the engine bay heats up, the fuel pump begins to cut out. At first it’s just a hint. But with more runs and more heat it gets worse and the engine cuts out more often and for longer on ensuing runs.
At one event the engine died while idling in grid and despite good cranking power it would not start until we let it sit for 10 minutes. Later, for last run it died again while waiting at the start line (after a long delay). Good cranking power but wouldn’t restart. My co-driver got a peak at the fuel pressure gauge during my cranking and noted it was at zero. Later, it restarted fine.
This past Saturday it was fine on a very short (23 second) test course. Took a dozen runs in 30 minutes. But it was not a heavy throttle course. On Sunday there was a long course with lots of long throttle sections. First few runs, again, were fine. Last run of the morning hinted at a very brief fuel cut out. We were back at it two hours later. First 2 runs of afternoon had one solid cut out each. Then with more runs, we experienced more cut outs until the last few runs of the day were incredibly compromised with many short and long fuel cut outs.
Here’s a video taken showing the fuel pressure gauge during one of those runs. In this one minute video the engine cuts out 3 or 4 times. https://youtu.be/NXRGPwCu4FU (The loose bolt you can see on the right doesn’t need to be there and will be removed. The gold covered line also on the right will be secured.)
Over the last few events I replaced the crankshaft position sensor and fuel pump relay. No help. Since the last event I replaced the 2 year old Bosch 044 fuel pump with an identical brand new one and will test it at the next event. But I don’t think that’s the issue because everything runs fine until the car heats up. Wouldn’t a fuel pump problem be consistent? Or can a fuel pump get fritzy due to heating up too much? The fuel pump location is less than a foot from one of the headers. At the last event I shielded it with commercially available heat shield material but it didn’t help.
Based on how fast the fuel pressure drops and how quickly it recovers (see video) it does seem like it has to be an electrical problem, yes? And the electrical system is over-taxed. Voltage below 11.8 will cause engine to misfire. But this situation isn’t a misfiring. This is loss of fuel pressure for ½ to 2 seconds per shot. Wouldn’t a battery voltage problem show a lot slower pressure drop than what we see in the video? Battery is brand new.
It looks like the engine is losing all or most of the voltage to the fuel pump momentarily and then it comes back again. So there’s an intermittent connection occurring but only with the addition of heat. It won’t happen on the first 3 or 4 runs of the day. I’m flummoxed.
I don’t see any loose connections or bad grounds or broken wires but I haven’t removed the wiring harness for a detailed examination. And has anyone experienced a bad connection/ground/wire only making itself apparent after the heat created by running the car for a while?
Another variable is that at some point this season I added a heat shield below the stock air intakes to try to reduce heat into the intake. So engine compartment temps might be higher but it’s not like it’s a sealed engine compartment. And even if it did heat up more than in the past, is there a component (fuel pump???) that just can’t take that extra 25 or 50 degrees? Yet I can’t ignore this factor. My plan is to run the car next weekend with the new fuel pump. See if the problem occurs. If it does, I’ll remove the heat shield (it’s just an 032 piece of aluminum above the headers and below the stock air intakes. Or should I just remove it right away? Then I wouldn’t know if that was the winning move or the fuel pump change did the job.
I’m wondering if I should just go ahead and get a new wiring harness.
Any thoughts on this issue will be much appreciated.