hard starting not what you think

[greenbus]

i moved my batteries to the bed of the truck and replaced them with some larger heavy duty (semi batteries) all wires are connected just as before batteries grounded to frame. engine grounded directly to frame.
I replaced old batteries because they tested 10.5v standing and 8.5 loaded one still gave 700 amps on load test but other bearly broke 200.
any way. first couple days after moving batteries everything was fine.
then my wait to start lite would be dim acompiede by a buzzzing ( fuel pump and injector driver realy (which i later found)) then it stops buzzing and lite is bright for a time (it varies) then turns off. try to start and it just cranks (normal speed not slow) and cranks and cranks i tried cycling the glow plugs but every time you do it repeats the above, and eventuly after 15 min of on off cranking it will start) I rechaged the batteries last nite, now it still buzzes along with dim wait lite for a few seconds then cycles normal and starts right up. average temp right now is about 35-37F. if i plug it in it starts easly also which is how i've made it by the past couple of days till i had a chance to work on it.
seems the lower the voltage (these batteries are 12.4 standing and we're 12.0 before) the longer the buzzing and lite stays dim. but if pluged in it buzzes for few seconds. then normaly operates.
i gave direct power to the injector driver , while the fuel pump relay still buzzed it started right away.

I'm thinking a bad ground and its tring to find it else where thus the relation to voltage. are the fuel pump realy and injector driver realy on the same ground, they are on the same fuse thus same circuit. if so where is this ground
thanks for reading.
Jake

[NotStock]

What gauge wire did you run to the batteries? It is possible you are not getting enough current transfer...

[greenbus]

same as stock size 3 ott

[250downunder]

How much longer are the cables? May be voltage drop over the extra length.

[szyd]

If it is cranking fine you are not loosing voltage. Like you said there is a bad ground or short in the system whren glows are heating. I would start by tracing glo wiring under valve covers the whole system may be you have a bad glo plug or 2. It would also help to know what year how many miles and any mods done to truck. So that a real tech can help you i am just shade tree.

[elibenson]

2 things. 1, If you have several more feet of cable, then you need to get the next size larger cable. 2, you have a grounding problem. You need to ground to the cab body, the frame and the engine its self. If not, BAD THINGS *will* happen. You'd be surprised where it chooses to ground. Like through your antenna, up the transmission shift cable(and through your steering column), Through your transmission cooler, it'll surprise you in a really bad way. The reason why it won't start with the glow plugs running is that there is not enough ground to go around. While they are running, there is so much current, that the wimpy ground you do have is all used up by the glow plugs, and the IDM/PCM aren't able to ground. Once the glow plug system shuts off, it frees up enough that other things start working.

I would definitely go and get a big heavy cable, and run it from the battery to the engine, battery to the frame, then battery to body, then also frame to engine, engine to body. That covers all possibilities.

I had a friend's small block chevorlet that was not grounded properly when he installed an MSD. It grounded through this distributor gear and down the shaft that drives his oil pump. Fried the shaft and welded the oil pump solid. He thought he had blown the engine when the pressure dropped, the lifters started making horrible noises and such. We finally grounded it like I said before, and it solved the problem (and installed a new pump and shaft, new distributor, new MSD).

[Justinlw]

Any time you relocate a battery you should still run a ground cable directly to the engine along with a local frame and body ground. Also, you should use a welding lead cable instead of the run of the mill stranded battery cable. Welding leads are much finer and more dense strands and show much less voltage drop over distance.

[greenbus]

ok its a late 99
i have stage 3 hybrids , intake , f5 chip, stealth stage 1
fass 95gph
moved the batteries so i could put i water to air intercooler
positive side of cable is 6 feet longer
i did use High quality fine strand its all we have here ( i work at a heavy truck shop)
engien grounded to frame batteries grounded to frame. cab grounded to frame in 3 places (2 factory) i added
i just started it after work today not pluged in 38 degrees
buzzed 1 sec then cycled normal and started normal (aprox 4-5 seconds of cranking)
checked GP's all good.
like i said only injector driver relay and fuel pump relay buzz momentarly
grounds are also 3 ott and only 3 feet or less each

3 ott is more than enough for the positive side. semis use 3 ott for their starts and pull mega amps come winter and semis all have their batteries on the frame rails thus atleast 8 feet of cable to starter