Reeking Havoc

hello all i'm at a loss here i have a 96 454 mag mpi that acts like it has a fuel problem. its in a twin app and star motor runs perfect and port did until last weekend. started to notice a ping sound over 2800 rpms but only when its in gear if i have it in neutral i can run it at a steady 4gs or so and sounds perfect! the only other thing that i've noticed is that on occasion the motor after you've been running awhile and shut it down sometimes it won't start and when it does it seems to run then you can hear the motor sucking some serious air and then dies? and it will do that up to 6 or 8 times then it will be fine? also star motor starts up first try everytime and the motor thats giving me probs seems to start then die then on the second try start and idle fine almost anytime cold, warm whatever. i've changed fuel water sep seemed fine no water put new one on, gas is fresh, pulled plugs to try to find lean cond and plugs looked great. last weekend when it started i just ran star motor a little higher than port and with some of the strain off of it i could run almost 50 with no probs. but once motor approached 2800 or 3000 rpms it would ping every few seconds or so. if you try to hammer it, it makes all kinds of noise not knocking i'm very fam with that sound it sounds to me like serious pinging? oil pressures perfect, oil looks fresh and free from anything. i read on here poss fuel reg prob? thought maybe somebody else has experienced this before. thanks in advance for all your guys help.

CMG

have you checked the timing on the motor?

Dave_N

Yes, check the timing. You will need to put the engine in "Base Timing Mode". A code or scan tool is normally used to do this, but you can just jump the "A" and "B" terminals on the Data Link Connector.

It does sound like your problem could be fuel delivery realted. You will need a fuel pressure gauge if you want to diagnose this any further. You want to see 36PSI, and it should be steady as the engine is brought up to operating RPM under load (where the problem is occuring).

Dave

Reeking Havoc

dist all tight so wouldn't see why it would have changed from one day to another. i imagine theres somewhere on the fuel rail to put a gauge? should it be at 36 at idle and then also as you run it up? also is the "scan/code" tool avail to purchase anywhere? thanks again for all your help guys take care

Dave_N

You can actually make a code tool if you wanted to. I did a thread a little while back about how to do it. Search on "EFI Code Tool" and you should find it. A code tool will also allow you to see if there are trouble codes present. If you don't want to make a code tool you can buy one for $40.00 at Rinda.com. They also sell scan tools (A lot better if you can afford one). Below is from the Mercruiser service manual for your engine.

Dave

Reeking Havoc

thanks guys for all your suggestions i finally got a gauge on it and its only reading about 26 psi but flucs alot so its def a fuel prob now from what i read it should be about 28 to 32? i just need to decifer if its a reg prob or a fuel pump prob or if some screen or something is clogged my motors don't have the cool flow on them so from what i hear it might be a little easier to figure out. i plugged to vac line and check again and the reg seems to be working from what i read there is a filter on the bottom of the high pressure pump so i guess i'll just take the whole thing out and apart and see if theres anything blocking the flow. thanks again guys