I am a novice mechanic trying to get my son’s swamped 1999 Blazer 4.3 CSFI running. The vehicle was running excellent with no issues at all before the bath. It was doused in swampy water up to the top of the engine for about an hour with the front end being the deepest. There was evidence of water on the CSFI injector electrical connection boot and I’m not sure if this may have caused any damage. However, the boot was completely dry on the inside. Water did enter the engine and was removed with an oil change and new plugs installed. I dropped the fuel tank, removed the pump and checked for any signs of water contamination. The tank and pump all checked out okay. I reinstalled the fuel pump and tank without any problems. I posted earlier on this vehicle concerning the fuel pump relay. I’ve checked all fuses and relays both in the engine compartment and the IP. All test okay. The fuel pump runs with “key on” and again with “key off” for 2 seconds as designed. The engine starts and runs smooth, but only for a second or two. So at this point I figured it is either an ignition or fuel problem.

I began by checking the fuel system first and here is what I’ve tried and observed thus far:
1). The pressure at “key on” is 62 psi, but immediately drops to 53 psi when the pump shuts off.
2). I reduced the pressure on the gauge to 10 psi and found no noticeable loss of pressure after 10 minutes. (This should eliminate the pump check valve leaking).
3). I jumpered the pump relay terminal to stay on during a few start attempts and found that the pressure dropped to about 54-53 psi when it fired, then returned to 62 psi after it stalled. (I figured that this would eliminate any question of power not being at the pump during and after the cranking).
4). I also found that I can keep the engine running with ether as long as I continue spraying.

I believe that these tests so far reduces the chance that it is an ignition related issue, so I am continuing my focus on the fuel system for now. I believe that the issue lies with either or both the FPR and/or the injectors based on the content that I have read in the “96+ (SCFI/MFI)FuelSystemDiagnosis” thread posted by swartlkkand also taking into account that there was evidence of water contamination to these components.

My next diagnosis step would be to use the fuel pipe shut-off adaptor attached near the fuel filter to further isolate the pressure drop, but I don’t own one and can’t find one. Any ideas where I can obtain one would be greatly appreciated. I would also appreciate any thoughts on what I’ve done so far and whether I am on the right track or missing something. My next move would be to replace the FPR if I can’t find a shut-off adaptor, but I really hate to guess or trial and error my way through this. Any and all assistance is greatly appreciated. Thanks in advance.

 

In my opinion, the ignition switch is still a viable root cause, but lets explore some other areas.

I would take some WD40 to any suspect electrical connections. This includes the electrical connection to the spider, the ICM/coil, and anything else that is suspect of having water intrusion. WD40 will displace the water. You will then be able to blow the excess WD40 out of the connection with some compressed air (or CO2 if you do not have a compressor).

Does the engine stall after running for the same amount of time consistently?

 

Yes, it runs for about the same period of time each try, unless I introduce ether. It does run long enough to register normal oil pressure also.

I have sprayed wire dryer in nearly all of the connectors, but not the spider. I will do that. Is WD-40 preferred over wire dryer?

Two other areas of concern from an electrical perspective is that the fuel gauge, gear selector display, odometer and all MIL (with the exception of the S.E.S. and the SIR) do not work on the IP cluster. The SIR was disabled per Chilton's directions. The IP took on water during the tow removal from the ditch. Could this be a cause for the symptoms and what are the issues (if any) from swaping out the IP with a used one?

I also removed an after market remote start unit (Crime Stopper) that was wired into the ignition wire harness. All wires are intact, but I was thinking about replacing the switch just to be safe. I will take your advice and do that.

Thanks for your help!

 

Is it safe to assume that the ignition switch also took on water? If so, I would replace that. The dash being dead is another sign pointing to the ignition switch.

And wire dryer should work just the same without the left over oily residue that WD40 has so you're good there.

 

I didn't see any signs of water at the switch, but the water was trapped in the vehicle with both doors closed when the tow truck pulled it out rear end first. This caused the water to settle forward as the rear end was lifted and the left front was still low in the ditch. It is very possible and likely that water reached the switch. I did spray all of the connections around the steering wheel with wire dryer. All of the wheel and stalk controls work (turn signal, hazzards, wipers, horn) but they seemed a bit sticky at first. I will replace the switch this weekend and give it another try. I will update at that time.

Thanks again for you help and the tip on the wire dryer.

 

I have installed a new ignition switch, but I am receiving the same results. The IP still does not fully function and the vehicle starts quickly and runs well for a second or two. I inspected and sprayed wire dryer in the engine compartment electrical connections. I didn't find any evidence of water intrusion into any of the weather sealed connectors. I also installed a new fuel filter to eliminate that.

I am still finding that the fuel pressure hits about 62 psi while the pump runs at "key on" then instantly drops to about 55/56 psi after 2 second pump cycle. During the starting phase, the psi goes to 62 at initial crank but then drops quickly to 52 psi and this is when it stalls out. Does this sound like a faulty FPR?

I just ordered a replacement IP cluster from ebay. Is there anything special that needs to be done to allow the swap of a used cluster unit, i.e. VCM programming?

Any ideas where to check next would be appreciated.